Systems and/or methods providing ePDCCH in a multiple carrier based and/or quasi-collated network

ABSTRACT

ePDCCH may be provided. For example, a WTRU may receive a configuration for monitoring an ePDCCH resource. Based on the configuration, the WTRU may be configured to monitor and may monitor the ePDCCH resource on a particular subframe. Additionally, a WTRU may derive an aggregation level for a subframe associated with an aggregation level number N AL . The WTRU may transmit or monitor an ePDCCH using the aggregation level associated with the N AL  for the subframe. A WTRU may also receive a reference signal. The WTRU may then determine the type of reference signal received. The WTRU may perform a demodulation of the PDSCH or ePDCCH using a demodulation timing based on the determined type. The ePDCCH or PDSCH may also be monitored or received by identifying a demodulation reference timing implicitly based on a location of one or more ePDCCH resources where the WTRU may receive DCI.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/751,114, filed Jan. 27, 2013, which claims the benefit of U.S.Provisional Patent Application Nos. 61/591,508 filed Jan. 27, 2012;61/612,834 filed Mar. 19, 2012; 61/688,164 filed May 9, 2012; 61/644,972filed May 9, 2012; 61/678,612 filed Aug. 1, 2012; 61/706,119 filed Sep.26, 2012; 61/720,646 filed Oct. 31, 2012; and 61/753,279 filed Jan. 16,2013, the contents of which are hereby incorporated by reference herein.

BACKGROUND

Current communication systems (e.g., a LTE/LTE-Advanced system) mayprovide multiple antennas, multiple component carriers, and/orquasi-collated antenna ports to support transmissions. Such multipleantennas, multiple component carriers, and/or quasi-collated antennaports may be provided for various purposes including peak systemthroughput enhancement, extended cell coverage, higher Doppler support,and the like. Unfortunately, such communication systems may provide anePDCCH design that may be focused on a single component carrier (e.g.,rather than multiple component carriers and/or multiple antennas) and/ormay not be suitable to support quasi-collated antenna ports such thatperformance in a multiple carrier system may be limited and/or may notbe adequately designed to avoid errors in frames and/or subframes (e.g.,special subframes), may have tighter PDSCH and/or CSI reportingprocessing times, may not provide suitable PUCCH resource allocation,may not provide a PDCCH indication during a configuration and/orreference symbols that may be quasi-collated with an antenna port maynot be provided at a sufficient time for use by ePDCCH and/or thedecoding thereof.

SUMMARY

Systems, methods, and instrumentalities may be disclosed to provideePDCCH in a multiple carrier communication system. For example, a UE orWTRU may receive a configuration for monitoring an ePDCCH resource.Based on such a configuration, the UE or WTRU may be configured tomonitor the ePDCCH resource on a particular subframe. The WTRU may thenmonitor the ePDCCH resource on the subframe. In example embodiments, thesubframe may not be a special subframe, the configuration may bereceived via higher layer signalling, the configuration may include oneor more PRB sets for monitoring on the ePDCCH resource where the PRBsets may include a set of eCCEs that include eREGs, further monitoring aPDCCH resource on a different subframe, demodulating the ePDCCHresource, and the like.

Systems, methods, and instrumentalities may also be disclosed forproviding an ePDCCH based on an aggregation level. For example, a UE orWTRU may derive an aggregation level (e.g., an eCCE aggregation level)for a subframe. The UE or WTRU may derive such an aggregation levelbased on an aggregation level number N_(AL) for the subframe where, inan embodiment, N_(AL) may be a positive integer. The UE or WTRU maytransmit or monitor an ePDCCH according to or using an aggregation levelassociated with the N_(AL) for the subframe. For example, if a searchspace is {1,2,4,8} and N_(AL) is 2, the UE or WTRU may monitor accordingto {2,4,8,16}.

Systems, methods, and instrumentalities may further be disclosed hereinfor receiving or monitoring ePDCCH or PDSCH. For example, a UE or WTRUmay receive a reference signal. The UE or WTRU may then determine thetype of reference signal received. The UE or WTRU may perform ademodulation of the PDSCH or ePDCCH using a demodulation timing based onthe type. For example, when the reference signal may be a channel stateinformation reference signal (CSI-RS), a PDSCH demodulation may beperformed using a demodulation reference timing based on a Fast FourierTransform (FFT) timing and a channel estimation coefficient associatedwith the CSI-RS. In additional embodiments, the ePDCCH or PDSCH may bemonitored by identifying a demodulation reference timing implicitlybased on a location of one or more ePDCCH resources where the UE or WTRUmay receive downlink control information (DCI).

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawings.

FIG. 1A depicts a diagram of an example communications system in whichone or more disclosed embodiments may be implemented.

FIG. 1B depicts a system diagram of an example wireless transmit/receiveunit (WTRU) that may be used within the communications systemillustrated in FIG. 1A.

FIG. 1C depicts a system diagram of an example radio access network andan example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 1D depicts a system diagram of another example radio access networkand an example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 1E depicts a system diagram of another example radio access networkand an example core network that may be used within the communicationssystem illustrated in FIG. 1A.

FIG. 2 illustrates an example embodiment of a WTRU or UE-specificprecoded DM-RS.

FIG. 3 illustrates an example embodiment of a non-precoded cell-specificRS.

FIG. 4 illustrates an example embodiment of a WTRU or UE-specific DM-RSfor normal CP (e.g., port 5).

FIG. 5 illustrates example embodiments of a CRS structure based on thenumber of antenna ports.

FIG. 6 illustrates an example embodiment of DM-RS pattern that maysupport, for example, eight layers.

FIG. 7 illustrates an example embodiment of CSI-RS patterns that may bereused based on the number of ports.

FIG. 8 illustrates an example embodiment of a positioning architecture.

FIG. 9 illustrates an example embodiment of a REG definition in adownlink control channel region with 2Tx CRS.

FIG. 10 illustrates an example embodiment of a REG definition in adownlink control channel region with 4Tx CRS.

FIG. 11 illustrates an example embodiment of PCFICH REG allocation basedon PCI.

FIG. 12 illustrates an example embodiment of PCFICH and PHICH REGallocation based on PCI.

FIG. 13 illustrates an example embodiment of ePDCCH multiplexing withPDSCH (e.g., FDM multiplexing).

FIG. 14 illustrates an example embodiment of a mapping to a physicalresource block for PUCCH.

FIG. 15 illustrates an example embodiment of a collision between DM-RSand PRS.

FIG. 16 illustrates an example embodiment of ePDCCH resource allocationin a subframe.

FIG. 17 illustrates an example embodiment of carrier aggregation withdifferent TDD UL-DL configuration(s).

FIG. 18 illustrates an example embodiment of CCE aggregation acrossmultiple carriers in distributed resource allocation.

FIG. 19 illustrates an example embodiment of a PRB-pair that may be usedfor ePDCCH transmission based on the number of antenna ports (e.g.,ports 7-10 and 7-8 respectively).

FIG. 20 illustrates an example embodiment of an eCCE-to-EREG mapping inePDCCH based on localized and/or distributed allocation.

FIG. 21 illustrates an example embodiment of an eCCE-to-eREG mappingwith contiguous allocation.

FIG. 22 illustrates an example embodiment of a block interleaver.

FIG. 23 illustrates an example embodiment of a hybrid allocation byusing a block interleaver.

FIG. 24 illustrates an example embodiment of a co-existence of localizedand/or distributed eCCEs.

FIG. 25 illustrates an example embodiment of an antenna port mapping foreREG and eCCE.

FIG. 26 illustrates an example embodiment of a common search spacedefinition in a legacy PDCCH region in a PCell.

DETAILED DESCRIPTION

A detailed description of illustrative embodiments may now be describedwith reference to the FIGS. However, while the embodiments herein may bedescribed in connection with exemplary embodiments, they should not belimited thereto and other embodiments may be used or modifications andadditions may be made to the described embodiments for performing thesame, or similar, functions of the disclosure without deviatingtherefrom. In addition, the FIGS. may illustrate call flows that may beexemplary. It should be understood that other embodiments may be used.The order of the flows may be varied. Also, flows may be omitted if notimplemented and additional flows may be added.

Systems and/or methods for providing an efficient downlink controlchannel design (e.g., an enhanced downlink control channel) in amulti-carrier based wireless network (e.g., such as the networkdescribed in FIGS. 1A-1E) may be disclosed. For example, such systemsand/or methods may provide and/or use localized and/or distributedresource allocation in multiple carrier system including, for example,distributed resource allocation across multiple component carriers maybe provided. Additionally, PDSCH and/or CSI feedback processing timerelaxation may be provided and/or used in such systems and/or methodsincluding flexible PDSCH processing time adaptation based on multiplecomponent carrier reception in combination with ePDCCH and/or flexibleCSI reporting time adaptation based on reporting bandwidth, the numberof component carriers, and the like. In an embodiment, such systemsand/or methods may further provide and/or use ePDCCH and/or legacyuplink control signaling relations including cross-carrier schedulingand/or a new allocation of an ePDCCH physical and/or logical address(e.g., a CCE index) for the relation of uplink control channels. TDDspecific embodiments for such systems and/or methods may also beprovided and/or used including ePDCCH usage in a special subframe and/orTDD inter-band. According to an example embodiment, a PDCCH fallbacktransmission mode may be provided and/or used for such systems and/ormethods where UE or WTRU behaviors of a PDCCH reception in an ambiguityperiod with a RRC-configured PDCCH configuration between legacy PDCCHand ePDCCH.

Additionally, such systems and/or methods may provide and/or use avariable eREG and/or eCCE definition including, for example, a full FDMbased eREG definition. Such systems and/or method may further provideand/or use an eCCE-to-eREG mapping based on an ePDCCH transmission mode,an interleaver design with a variable eREG and/or eCCE definition, anadaptive eREG-to-eCCE mapping (e.g., a variable number of eREGs per eCCEaccording to a reference signal overhead in a subframe), and the like.In an embodiment, an antenna port association for eREG and/or eCCE maybe provided and/or used in such systems and/or methods including alocation and/or aggregation level based antenna port mapping and/or aPRG size definition for PRB-bundling. An ePDCCH search space designincluding, for example, a common search space and/or a WTRU orUE-specific search space, a TBS restriction according to a TA and/or CSIfeedback request, and/or a PUCCH allocation based on an ePDCCH withmultiple downlink component carriers may also be provided and/or usedwith such systems and/or methods.

According to an embodiment, such systems and/or methods may provideand/or use an antenna port association with a WTRU or UE-specificconfiguration including combinations of a RE-position based mappingand/or a WTRU or UE-specific configuration and/or antenna port mappingrules based on a common search space and WTRU or UE-specific searchspace in a distributed transmission. In an embodiment, collisionhandling between ePDCCH resources and legacy signals other than PDSCHincluding rate-matching and/or puncturing rules may be provided and/orused for such systems and/or methods. Additionally, adaptiveeREG-to-eCCE mapping, a mapping rule based on a subframe characteristic,and the like may be provided and/or used. In additional embodiments, aTBS restriction in a TDD mode according to a HARQ-ACK timing may beprovided and/or used.

Such systems and/or methods may further provide and/or use an ePDCCHresource. For example, multiple ePDCCH resource sets with variableresource sizes per set may be provided and/or used depending on thesystem bandwidth including a downlink control information (DCI) formatdependent on ePDCCH candidates, an ePDCCH resource set dependent on ahashing function, and/or an ePCFICH indication of the number of ePDCCHresource sets.

PUCCH (A/N) resource allocation for ePDCCH may also be provided and/orused (e.g., in such systems and/or methods) including support forMU-MIMO.

In an embodiment, such systems and/or methods may also provide PRScollision handling techniques including broadcasting PRS configurationinformation and/or providing WTRU or UE behaviors when ePDCCH resourcesmay collide with a PRS.

Multiple ePDCCH resource sets for a multiple carrier system may furtherbe provided and/or defined by such systems and/or methods. For example,a DM-RS sequence may be defined. In such an embodiment, A DM-RS sequencegenerator (XID) may be provided, used, and/or defined per ePDCCH set orfor each ePDCCH set. Additionally, when a WTRU or UE may receive a PDSCHassociated with an ePDCCH, the same XID received from ePDCCH may be usedfor PDSCH demodulation. In additional embodiments, PUCCH resourceallocation with multiple ePDCCH resource sets may be provided and/orused and/or a search space definition of localized transmissionsincluding an ePDCCH transmission specific hash function definitionand/or ePDCCH transmission specific eCCE indexing such as different eCCEindexing according to or based on an aggregation level may be providedand/or used. eREG-to-eCCE mapping may also be provided and/or used. Forexample, a cell-specific eREG-to-eCCE mapping based on the localized anddistributed transmissions may be provided and/or used. In an embodiment,supported transmission modes associated with ePDCCH may also be providedand/or defined including, for example, a subset of transmission modessupported by ePDCCH and/or (e.g., according to the transmission scheme)the supportable ePDCCH type (e.g., localized and distributed) that maybe different.

Additionally, such systems and/or methods may provide ePDCCH a WTRU orUE-specific search space (e.g., an equation associated therewith) and ahash function. For example, a search space equation for localized anddistributed ePDCCH and/or a hash function with multiple ePDCCH sets maybe provided and/or used.

Such systems and/or methods may further provide an ePDCCH common searchspace including an eREG/eCCE definition for the common search space,starting symbol (e.g., associated therewith), a resourcedefinition/configuration, and/or support for overlapping resourcesbetween UE-specific search space and common search space.

Systems and methods providing a demodulation reference timing indicationmay be disclosed. For example, single demodulation reference timingsupport and multiple demodulation reference timing support such asresource specific demodulation reference timing and an indication of ademodulation reference timing (e.g., a demodulation reference timingindication) may be provided as described herein.

FIG. 1A is a diagram of an example communications system 100 in whichone or more disclosed embodiments may be implemented. The communicationssystem 100 may be a multiple access system that provides content, suchas voice, data, video, messaging, broadcast, etc., to multiple wirelessusers. The communications system 100 may enable multiple wireless usersto access such content through the sharing of system resources,including wireless bandwidth. For example, the communications systems100 may employ one or more channel access methods, such as code divisionmultiple access (CDMA), time division multiple access (TDMA), frequencydivision multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrierFDMA (SC-FDMA), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, and/or 102 d (whichgenerally or collectively may be referred to as WTRU 102), a radioaccess network (RAN) 103/104/105, a core network 106/107/109, a publicswitched telephone network (PSTN) 108, the Internet 110, and othernetworks 112, though it will be appreciated that the disclosedembodiments contemplate any number of WTRUs, base stations, networks,and/or network elements. Each of the WTRUs 102 a, 102 b, 102 c, 102 dmay be any type of device configured to operate and/or communicate in awireless environment. By way of example, the WTRUs 102 a, 102 b, 102 c,102 d may be configured to transmit and/or receive wireless signals andmay include user equipment (UE), a mobile station, a fixed or mobilesubscriber unit, a pager, a cellular telephone, a personal digitalassistant (PDA), a smartphone, a laptop, a netbook, a personal computer,a wireless sensor, consumer electronics, and the like.

The communications systems 100 may also include a base station 114 a anda base station 114 b. Each of the base stations 114 a, 114 b may be anytype of device configured to wirelessly interface with at least one ofthe WTRUs 102 a, 102 b, 102 c, 102 dto facilitate access to one or morecommunication networks, such as the core network 106/107/109, theInternet 110, and/or the networks 112. By way of example, the basestations 114 a, 114 b may be a base transceiver station (BTS), a Node-B,an eNode B, a Home Node B, a Home eNode B, a site controller, an accesspoint (AP), a wireless router, and the like. While the base stations 114a, 114 b may be each depicted as a single element, it will beappreciated that the base stations 114 a, 114 b may include any numberof interconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 103/104/105, which mayalso include other base stations and/or network elements (not shown),such as a base station controller (BSC), a radio network controller(RNC), relay nodes, etc. The base station 114 a and/or the base station114 b may be configured to transmit and/or receive wireless signalswithin a particular geographic region, which may be referred to as acell (not shown). The cell may further be divided into cell sectors. Forexample, the cell associated with the base station 114 a may be dividedinto three sectors. Thus, in one embodiment, the base station 114 a mayinclude three transceivers, i.e., one for each sector of the cell. Inanother embodiment, the base station 114 a may employ multiple-inputmultiple output (MIMO) technology and, therefore, may utilize multipletransceivers for each sector of the cell.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 115/116/117,which may be any suitable wireless communication link (e.g., radiofrequency (RF), microwave, infrared (IR), ultraviolet (UV), visiblelight, etc.). The air interface 115/116/117 may be established using anysuitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 103/104/105 and the WTRUs 102a, 102 b, 102 c may implement a radio technology such as UniversalMobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA),which may establish the air interface 115/116/117 using wideband CDMA(WCDMA). WCDMA may include communication protocols such as High-SpeedPacket Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may includeHigh-Speed Downlink Packet Access (HSDPA) and/or High-Speed UplinkPacket Access (HSUPA).

In another embodiment, the base station 114 a and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Evolved UMTSTerrestrial Radio Access (E-UTRA), which may establish the air interface115/116/117 using Long Term Evolution (LTE) and/or LTE-Advanced (LTE-A).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.16 (i.e.,Worldwide Interoperability for Microwave Access (WiMAX)), CDMA2000,CDMA2000 1×, CDMA2000 EV-DO, Interim Standard 2000 (IS-2000), InterimStandard 95 (IS-95), Interim Standard 856 (IS-856), Global System forMobile communications (GSM), Enhanced Data rates for GSM Evolution(EDGE), GSM EDGE (GERAN), and the like.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, and the like. In oneembodiment, the base station 114 b and the WTRUs 102 c, 102 d mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In another embodiment, the base station 114 band the WTRUs 102 c, 102 d may implement a radio technology such as IEEE802.15 to establish a wireless personal area network (WPAN). In yetanother embodiment, the base station 114 b and the WTRUs 102 c, 102 dmay utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, etc.) to establish a picocell or femtocell. As shown in FIG. 1A,the base station 114 b may have a direct connection to the Internet 110.Thus, the base station 114 b may not be required to access the Internet110 via the core network 106/107/109.

The RAN 103/104/105 may be in communication with the core network106/107/109, which may be any type of network configured to providevoice, data, applications, and/or voice over internet protocol (VoIP)services to one or more of the WTRUs 102 a, 102 b, 102 c, 102 d. Forexample, the core network 106/107/109 may provide call control, billingservices, mobile location-based services, pre-paid calling, Internetconnectivity, video distribution, etc., and/or perform high-levelsecurity functions, such as user authentication. Although not shown inFIG. 1A, it will be appreciated that the RAN 103/104/105 and/or the corenetwork 106/107/109 may be in direct or indirect communication withother RANs that employ the same RAT as the RAN 103/104/105 or adifferent RAT. For example, in addition to being connected to the RAN103/104/105, which may be utilizing an E-UTRA radio technology, the corenetwork 106/107/109 may also be in communication with another RAN (notshown) employing a GSM radio technology.

The core network 106/107/109 may also serve as a gateway for the WTRUs102 a, 102 b, 102 c, 102 d to access the PSTN 108, the Internet 110,and/or other networks 112. The PSTN 108 may include circuit-switchedtelephone networks that provide plain old telephone service (POTS). TheInternet 110 may include a global system of interconnected computernetworks and devices that use common communication protocols, such asthe transmission control protocol (TCP), user datagram protocol (UDP)and the internet protocol (IP) in the TCP/IP internet protocol suite.The networks 112 may include wired or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another core network connected to one or moreRANs, which may employ the same RAT as the RAN 103/104/105 or adifferent RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, i.e., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks. For example, the WTRU 102 c shown in FIG. 1A may be configured tocommunicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram of an example WTRU 102. As shown in FIG. 1B,the WTRU 102 may include a processor 118, a transceiver 120, atransmit/receive element 122, a speaker/microphone 124, a keypad 126, adisplay/touchpad 128, non-removable memory 130, removable memory 132, apower source 134, a global positioning system (GPS) chipset 136, andother peripherals 138. It will be appreciated that the WTRU 102 mayinclude any sub-combination of the foregoing elements while remainingconsistent with an embodiment. Also, embodiments contemplate that thebase stations 114 a and 114 b, and/or the nodes that base stations 114 aand 114 b may represent, such as but not limited to transceiver station(BTS), a Node-B, a site controller, an access point (AP), a home node-B,an evolved home node-B (eNodeB), a home evolved node-B (HeNB), a homeevolved node-B gateway, and proxy nodes, among others, may include someor all of the elements depicted in FIG. 1B and described herein.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 1Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 115/116/117. For example, in one embodiment,the transmit/receive element 122 may be an antenna configured totransmit and/or receive RF signals. In another embodiment, thetransmit/receive element 122 may be an emitter/detector configured totransmit and/or receive IR, UV, or visible light signals, for example.In yet another embodiment, the transmit/receive element 122 may beconfigured to transmit and receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 1B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in one embodiment, the WTRU 102 mayinclude two or more transmit/receive elements 122 (e.g., multipleantennas) for transmitting and receiving wireless signals over the airinterface 115/116/117.

The transceiver 120 may be configured to modulate the signals that maybe to be transmitted by the transmit/receive element 122 and todemodulate the signals that may be received by the transmit/receiveelement 122. As noted above, the WTRU 102 may have multi-modecapabilities. Thus, the transceiver 120 may include multipletransceivers for enabling the WTRU 102 to communicate via multiple RATs,such as UTRA and IEEE 802.11, for example.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 115/116/117from a base station (e.g., base stations 114 a, 114 b) and/or determineits location based on the timing of the signals being received from twoor more nearby base stations. It will be appreciated that the WTRU 102may acquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, and the like.

FIG. 1C is a system diagram of the RAN 103 and the core network 106according to an embodiment. As noted above, the RAN 103 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102 cover the air interface 115. The RAN 103 may also be in communicationwith the core network 106. As shown in FIG. 1C, the RAN 103 may includeNode-Bs 140 a, 140 b, 140 c, which may each include one or moretransceivers for communicating with the WTRUs 102 a, 102 b, 102 c overthe air interface 115. The Node-Bs 140 a, 140 b, 140 c may each beassociated with a particular cell (not shown) within the RAN 103. TheRAN 103 may also include RNCs 140 a, 140 b. It will be appreciated thatthe RAN 103 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 1C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 140 a. Additionally, the Node-B 140 c may be incommunication with the RNC140 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 140 a, 142 b via an Iub interface.The RNCs 140 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 140 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 140 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macrodiversity, security functions, data encryption, and thelike.

The core network 106 shown in FIG. 1C may include a media gateway (MGW)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements may be depicted as part of the core network 106,it will be appreciated that any one of these elements may be ownedand/or operated by an entity other than the core network operator.

The RNC 142 a in the RAN 103 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices.

The RNC 142 a in the RAN 103 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatmay be owned and/or operated by other service providers.

FIG. 1D is a system diagram of the RAN 104 and the core network 107according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the core network 107.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 1D, theeNode-Bs 160 a, 160 b, 160 c may communicate with one another over an X2interface.

The core network 107 shown in FIG. 1D may include a mobility managemententity (MME) 162, a serving gateway 164, and a packet data network (PDN)gateway 166. While each of the foregoing elements may be depicted aspart of the core network 107, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 162 may be connected to each of the eNode-Bs 160 a, 160 b, 160 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may also provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 164 may be connected to each of the eNode-Bs 160 a,160 b, 160 c in the RAN 104 via the S1 interface. The serving gateway164 may generally route and forward user data packets to/from the WTRUs102 a, 102 b, 102 c. The serving gateway 164 may also perform otherfunctions, such as anchoring user planes during inter-eNode B handovers,triggering paging when downlink data is available for the WTRUs 102 a,102 b, 102 c, managing and storing contexts of the WTRUs 102 a, 102 b,102 c, and the like.

The serving gateway 164 may also be connected to the PDN gateway 166,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 107 may facilitate communications with other networks.For example, the core network 107 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 107 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 107 and the PSTN 108. In addition, the corenetwork 107 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatmay be owned and/or operated by other service providers.

FIG. 1E is a system diagram of the RAN 105 and the core network 109according to an embodiment. The RAN 105 may be an access service network(ASN) that employs IEEE 802.16 radio technology to communicate with theWTRUs 102 a, 102 b, 102 c over the air interface 117. As will be furtherdiscussed below, the communication links between the differentfunctional entities of the WTRUs 102 a, 102 b, 102 c, the RAN 105, andthe core network 109 may be defined as reference points.

As shown in FIG. 1E, the RAN 105 may include base stations 180 a, 180 b,180 c, and an ASN gateway 182, though it will be appreciated that theRAN 105 may include any number of base stations and ASN gateways whileremaining consistent with an embodiment. The base stations 180 a, 180 b,180 c may each be associated with a particular cell (not shown) in theRAN 105 and may each include one or more transceivers for communicatingwith the WTRUs 102 a, 102 b, 102 c over the air interface 117. In oneembodiment, the base stations 180 a, 180 b, 180 c may implement MIMOtechnology. Thus, the base station 180 a, for example, may use multipleantennas to transmit wireless signals to, and receive wireless signalsfrom, the WTRU 102 a. The base stations 180 a, 180 b, 180 c may alsoprovide mobility management functions, such as handoff triggering,tunnel establishment, radio resource management, traffic classification,quality of service (QoS) policy enforcement, and the like. The ASNgateway 182 may serve as a traffic aggregation point and may beresponsible for paging, caching of subscriber profiles, routing to thecore network 109, and the like.

The air interface 117 between the WTRUs 102 a, 102 b, 102 c and the RAN105 may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, 102 cmay establish a logical interface (not shown) with the core network 109.The logical interface between the WTRUs 102 a, 102 b, 102 c and the corenetwork 109 may be defined as an R2 reference point, which may be usedfor authentication, authorization, IP host configuration management,and/or mobility management.

The communication link between each of the base stations 180 a, 180 b,180 c may be defined as an R8 reference point that includes protocolsfor facilitating WTRU handovers and the transfer of data between basestations. The communication link between the base stations 180 a, 180 b,180 c and the ASN gateway 182 may be defined as an R6 reference point.The R6 reference point may include protocols for facilitating mobilitymanagement based on mobility events associated with each of the WTRUs102 a, 102 b, 102 c.

As shown in FIG. 1E, the RAN 105 may be connected to the core network109. The communication link between the RAN 105 and the core network 109may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 109 may include a mobile IP home agent(MIP-HA) 184, an authentication, authorization, accounting (AAA) server186, and a gateway 188. While each of the foregoing elements may bedepicted as part of the core network 109, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MIP-HA may be responsible for IP address management, and may enablethe WTRUs 102 a, 102 b, 102 c to roam between different ASNs and/ordifferent core networks. The MIP-HA 184 may provide the WTRUs 102 a, 102b, 102 c with access to packet-switched networks, such as the Internet110, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand IP-enabled devices. The AAA server 186 may be responsible for userauthentication and for supporting user services. The gateway 188 mayfacilitate interworking with other networks. For example, the gateway188 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. In addition, the gateway 188 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 112,which may include other wired or wireless networks that may be ownedand/or operated by other service providers.

Although not shown in FIG. 1E, it should be appreciated that the RAN 105may be connected to other ASNs and the core network 109 may be connectedto other core networks. The communication link between the RAN 105 theother ASNs may be defined as an R4 reference point, which may includeprotocols for coordinating the mobility of the WTRUs 102 a, 102 b, 102 cbetween the RAN 105 and the other ASNs. The communication link betweenthe core network 109 and the other core networks may be defined as an R5reference, which may include protocols for facilitating interworkingbetween home core networks and visited core networks.

According to an example embodiment, collaborative and/or multipleantenna transmissions may be provided in a communication system (e.g., aLTE/LTE-Advanced system) such as the communication system 100 describedabove with respect to FIGS. 1A-1E. In embodiments, such collaborativetransmissions may be provided and/or used such that a PDSCH transmissionfor a WTRU or UE (e.g., a LTE-A WTRU or UE) may be dynamically changedbetween transmission points without a cell selection/re-selectionprocedure. A WTRU or UE-specific RS based downlink control channeltransmission may also be provided and/or used, for example, to enhancePDCCH performance.

Additionally, such multiple antenna transmissions may be provided and/orused for various purposes including peak system throughput enhancement,extended cell coverage and high Doppler support. For example,single-user multiple-input multiple-output (SU-MIMO) may be used in suchthe communication system to increase peak and/or average user equipment(UE) or WTRU throughput. Additionally, multi-user MIMO may be used insuch a communication system to improve peak and/or average systemthroughput by exploiting multi-user diversity gain. Table 1 illustratesexample MIMO capabilities that may be used in a wireless communicationsystem to improve throughput, diversity gain, and the like.

TABLE 1 Example MIMO Capabilities in a Communication System (e.g., inLTE/LTE-Advanced) 3GPP E-UTRA Key Downlink MIMO LTE LTE-AdvancedTechniques Release 8 Release 9 Release 10 DL SU- Up to 4 streams Up to 4streams Up to 8 streams MIMO MU- Up to 2 users Up to 4 users Up to 4users MIMO (unitary (non-unitary (non-unitary precoding) precoding)precoding) UL SU- 1 stream 1 stream Up to 4 streams MIMO MU- Up to 8users Up to 8 users Up to 8 users MIMO

To assist with the MIMO performance (e.g., according to or based on WTRUor UE channel environments), up to, for example, nine transmission modeshave been employed. Such transmission modes may include a transmitdiversity mode, an open-loop spatial multiplexing mode, a closed-loopspatial multiplexing mode, and the like. Additionally, MIMO linkadaption may be used and/or provided. In embodiments, a WTRU or UE mayreport channel-state information (CSI) of multiple transmit antennaports to enable or facilitate such a MIMO link adaptation.

For example, a reference signal may be provided and/or used, forexample, with the CSI. In an embodiment, a reference signal may beprovided as or classified to a WTRU or UE-specific reference signal(WTRU or UE-RS) and/or a cell-specific reference signal (CRS). Accordingto an embodiment, the WTRU or UE-RS may be used for a specific WTRU orUE such that the RS may be transmitted for the resources allocated tothe WTRU or UE. Additionally, in an embodiment, the CRS may be acell-specific reference signal that may be shared by each of the UEs inthe cell such that the RS may be transmitted in a wideband manner.

According to or based on use, a reference signal (RS) may be, forexample, differentiated to a demodulation reference signal (DM-RS)and/or a channel-state-information reference signal (CSI-RS). The DM-RSmay be used for a particular WTRU or UE and the RS may be precoded toexploit beamforming gain. In an embodiment, the WTRU or UE-specificDM-RS may not be shared with other UEs in the cell. As such, the DM-RSmay be transmitted in the time and/or frequency resources allocated forthe WTRU or UE. Additionally, the DM-RS may be limited for use withdemodulation.

FIG. 2 illustrates an example embodiment of providing a WTRU orUE-specific precoded DM-RS. As shown in FIG. 2, if a precoded DM-RS maybe employed, the RS may be precoded using a precoding used for the datasymbol and the number of RS sequences corresponding to the number oflayers K may be transmitted. In an embodiment, K may be equal to orsmaller than physical antenna ports N_(T). Additionally, the K streamsin FIG. 2 may be allocated for a WTRU or UE or shared with multiple UEs.If multiple UEs may share the K streams, the co-scheduled UEs may sharethe same time/frequency resources at the same time.

As described above, a cell-specific reference signal (CRS) may beprovided and/or used. According to an example embodiment, the CRS may bedefined for the UEs in a cell and may be used for demodulation and/ormeasurement. Additionally, in example embodiments, the CRS may be sharedby UEs. In such an embodiment (e.g., since the CRS may be shared by theUEs), non-precoded RS may be used and/or employed, for example, to keepuniform cell coverage. The precoded RS may have different cell coverageaccording to the directions and/or due to a beamforming effect. FIG. 3shows an example embodiment of a MIMO transmitter that may be used for anon-precoded CRS transmission as described herein.

Additionally, in example embodiments, antenna virtualization may beprovided and/or used. For example, if the number of the physical antennaport and logical antenna port may be different, antenna virtualizationmay be used (e.g., with CRS and/or the non-precoded CRS transmissionshown in FIG. 3). RS sequences may also be transmitted for antenna portsirrespective of the number of streams.

According to example embodiments, different structures for DM-RS and/orCRS may be provided and/or used. FIG. 4 shows an example embodiment of aDM-RS (e.g., an antenna port-5) structure that may be used (e.g., in anLTE system) to support non-codebook based transmission. In anembodiment, the structure shown in FIG. 4 may be used at an eNB, forexample, where the antenna port-5 may be limited supporting one layertransmission. Additionally, the antenna port-5 shown in FIG. 4 may betransmitted with a CRS and, as such, the RS overhead (e.g., in total)may increase.

FIG. 5 shows an example embodiment of a CRS structure according to orbased on a number of antenna ports. The CRS patterns (e.g., shown inFIG. 5) for each antenna port may be mutually orthogonal in the timeand/or frequency domain. As shown in FIG. 5, R0 and R1 may indicate CRSfor antenna port 0 and antenna port 1 respectively. In an embodiment, toavoid interference between CRS antenna ports, the data REs that may belocated at the RE where a CRS antenna ports may be transmitted may bemuted.

According to example embodiments, a predefined sequence (e.g., aPseudo-random (PN), an m-sequence, and the like) may be multiplied withdownlink RS that may minimize inter-cell interference and/or may improvechannel estimation accuracy associated with CRS. The PN sequence may beapplied at an OFDM symbol level in a subframe and the sequence may bedefined according to the cell-ID, subframe number, the position of OFDMsymbol, and the like. For example, the number of CRS antenna ports maybe two, for example, in an OFDM symbol that may include a CRS per PRBand the number PRB in a communication system such as an LTE system mayvary from 6 to 110. In such an embodiment, the total number of CRS foran antenna port in an OFDM symbol that may include a RS may be 2×N_(RB),which may imply that the sequence length may be 2×N_(RB). Additionally,in such an embodiment, N_(RB) may denote the number of RBs correspondingto a bandwidth and the sequence may be binary or complex. The sequencer(m) may provide the complex sequence as follows

${{r(m)} = {{\frac{1}{\sqrt{2}}( {1 - {2 \cdot {c( {2m} )}}} )} + {j\frac{1}{\sqrt{2}}( {1 - {2 \cdot {c( {{2m} + 1} )}}} )}}},{m = 0},1,\ldots\mspace{14mu},{{2N_{RB}^{\max}} - 1}$where N_(RB) ^(max) may denote the number of RBs corresponding to amaximum bandwidth in a communication system such as an LTE system,N_(RB) ^(max) may be 110. Additionally, c may denote a PN sequence withlength-31 and may be defined with a Gold-sequence. If a DM-RS may beconfigured, the following equation may be used:

${{r(m)} = {{\frac{1}{\sqrt{2}}( {1 - {2 \cdot {c( {2m} )}}} )} + {j\frac{1}{\sqrt{2}}( {1 - {2 \cdot {c( {{2m} + 1} )}}} )}}},{m = 0},1,\ldots\mspace{14mu},{{12N_{RB}^{PDSCH}} - 1}$where N_(RB) ^(PDSCH) may denote a number of RBs allocated for aspecific WTRU or UE. The sequence length may vary according to thenumber RBs allocated for a WTRU or UE.

In an embodiment, a reference signal (RS) structure may also be provided(e.g., in 3GPP LTE-A). For example, to reduce the overall RS overhead, aDM-RS based downlink transmission may be used (e.g., in a communicationsystem such as in LTE-A). Additionally, the CRS-based downlinktransmission may transmit RS sequences for the physical antenna ports.As such, the DM-RS based downlink transmission may reduce the RSoverhead considering that the number of RSs that may be provided or usedfor DM-RS may be the same as the number of layers. Additionally,according to an embodiment, the number of layers may be equal to orsmaller than the number of physical antenna ports. FIG. 6 shows anexample embodiment of DM-RS patterns in a PRB for a subframe (e.g., aDM-RS pattern supporting up to 8 layers) that may be provided and/orused.

In embodiments, two CDM groups may be used for multiplexing, forexample, up to 4 layers in each CDM group such that up to 8 layers maybe multiplexed as a maximum in this pattern. For CDM multiplexing ofeach CDM group, 4×4 Walsh spreading may also be used.

Additionally, since the DM-RS may be used for demodulation performance(e.g., may be limited to being used for demodulation performance), atime and/or frequency sparse CSI-RS may be provided, for example, formeasurements. The CSI-RS may be transmitted with a duty cycle such as{5, 10, 20, 40, 80} ms in the PDSCH region. In addition, up to 20 CSI-RSpatterns for reuse may be available in a subframe. FIG. 7 illustrates anexample embodiment of CSI-RS patterns for reuse according to the numberof ports (e.g., where up to 20 CSI-RS patterns may be reused). In FIG.7, the same patterns or shading with a corresponding TX number includedtherein or associated therewith may represent the same set of REs for aCSI-RS configuration.

Observed Time Difference of Arrival (OTDOA) may also be provided and/orused, for example, for positioning, in a communication system such as anLTE system. For OTDOA positioning, a WTRU or UE may receive one or moresignals from a reference cell and/or one or more additional cells, forexample, neighbor cells, may measure the observed time differences ofarrival of these signals (e.g., between each additional or neighbor celland the reference cell), and/or may report such measurements,information or signals to the network. Based on the locations of thecells, timing differences among them which may be fixed, and/or otherinformation, the network may derive the WTRU or UE position by a meanssuch as trilateration or triangulation (e.g., assuming the WTRU or UEmay measure at least three cells) and/or by other methods or techniquesthat may provide a location and/or position. The reference cell may beor may not be a serving cell, for example a serving cell of the WTRU orUE. For example, the reference cell may be the serving cell of the WTRUor UE if the WTRU or UE may have one serving cell which may, forexample, be in the case of no carrier aggregation (CA). In anotherexample, the reference cell may be a serving cell such as a primarycell, PCell, which may be, for example, in the case of carrieraggregation. In an embodiment, the time difference of arrival may bemeasured based on a known signal. For example (e.g., for LTE), the WTRUor UE may use the cell-specific reference symbols (CRS) for suchmeasurements and/or, for a cell that may transmit the positioningreference signal (PRS), for example, the WTRU or UE may use the PRS. Toperform positioning measurements, the WTRU or UE may receive supportinginformation or assistance data such as information associated with thecells and/or signals to be measured. For OTDOA, the assistance data mayinclude PRS related parameters. In example embodiments, support of OTDOAby a WTRU or UE may be optional and the use of CRS or PRS for a givencell may be provided and/or decided by WTRU or UE implementations.

In an example embodiment, a positing reference signal (PRS) may betransmitted by the eNB such that the eNB may be aware of or may know itstransmission parameters for cells under its control. For a given cell,PRS may be defined to be provided or included in N_(PRS) consecutivedownlink subframes for each positioning instance (e.g., a PRSpositioning occasion) where, for example, the first subframe of theN_(PRS) downlink subframes may satisfy or provide(10×n_(f)+└n_(s)/2┘−Δ_(PRS))modT_(PRS)=0. According to an exampleembodiment, N_(PRS) may be 1, 2, 4, and/or 6 subframes and theparameters T_(PRS) and Δ_(PRS) may be the PRS periodicity and PRS offsetrespectively. Additionally, the PRS periodicity may be 160, 320, 640,and/or 1280 subframes and the PRS offset may be a value between 0 andthe PRS periodicity minus 1 or one less than the PRS periodicity. ThePRS bandwidth (BW) may be narrowband or wideband such that the PRS BWmay occupy a partial BW (e.g., part of the full or entire BW) of thecell and/or the full BW of the cell. The BW values may include, forexample, 6, 15, 25, 50, 75, and/or 100 resource blocks (RBs). In anembodiment, when the PRS may occupy a partial BW, the RBs may be in thecenter of the band or at any other suitable location within the band.Parameters which may be used for, provided for, defined for, and/or usedto define the PRS (e.g., which may be referred to as PRS informationand/or prs-info) for a cell may include one or more of the following:the number of DL subframes (e.g., N_(PRS)); a PRS configuration index(e.g., 0 to 4095) that may be used (e.g., in a table or other suitablestructure) to obtain T_(PRS) and Δ_(PRS) (e.g., the PRS periodicity andoffset); the PRS BW; PRS muting information that may define when PRSoccasions may be muted (e.g., not transmitted) in the cell; and thelike.

According to an embodiment, PRS positioning occasions may be muted in acell, for example, periodically. The PRS muting configuration may bedefined by a periodic PRS muting sequence that may have a periodicity of2, 4, 8, and/or 16 positioning occasions in embodiments. The PRS mutinginformation may be provided using a p-bit field for periodicity p whereeach bit may correspond to a PRS positioning occasion in each mutingsequence and/or may indicate whether that occasion may be muted or not.When a PRS positioning occasion may be muted in a cell, PRS may not betransmitted in the N_(PRS) subframes (e.g., any of the N_(PRS)subframes) of the particular occasion in that cell.

Additionally, when the PRS muting information may be signaled to a WTRUor UE in the positioning assistance data (e.g., when the PRS mutinginformation may be included in positing assistance data and signaledtherewith), the first bit of the PRS muting sequence may correspond tothe first PRS positioning occasion that may start after the beginning ofthe system frame number (SFN) being zero (e.g., SFN=0) where the SFN maybe the SFN of the WTRU's or UE's OTDOA reference cell.

FIG. 8 illustrates an example embodiment of an architecture that may beused for positioning. According to an embodiment, the architecture shownin FIG. 8 may be used with an LTE communication system such as thecommunication systems 100 shown FIGS. 1A and 1C-1E and may providepositioning for the LTE communication system. As shown in FIG. 8,positioning of or by a UE or WTRU may be controlled by an EnhancedServing Mobile Location Center (E-SMLC). In an example embodiment, thecommunication between the WTRU and E-SMLC may be point-to-point and/ortransparent to an eNB. The WTRU or UE may communicate with the E-SMLCusing a protocol such as the LTE Positioning Protocol (LPP) over thecontrol plane or the data plane as shown in FIG. 8. Such a communication(e.g., between the WTRU or UE and E-SMLC) may be encapsulated insignaling or data between the eNB and the WTRU or UE or between a SecureUser Plane Location (SUPL) Location Platform (SLP) and the WTRU or UE.According to an example embodiment, the eNB may not see what may beinside the LPP messages. The communication between the E-SMLC and theWTRU may pass through a Mobility Management Entity (MME) or a SLP wherethe MME or SLP may direct the communication to and/or from theappropriate WTRU and may or may not see the contents of thecommunication and may or may not modify the contents and/or thetransport of the communication. Communication may be possible or enabledvia the SLP and/or may be via a SUPL bearer if the WTU or UE may be aSUPL Enabled Terminal (SET).

Additionally, the information that may pass or be exchanged between theWTRU or UE and the E-SMLC may include one or more of the capability ofthe WTRU or UE to support OTDOA positioning, instructions from theE-SMLC to perform OTDOA measurements, OTDOA positioning assistance datafrom the E-SMLC to the WTRU or UE such as which cells are the referenceand/or additional or neighbor cells for OTDOA, and measurement reportsfrom the WTRU or UE to the E-SMLC. Assistance data or other exchangedinformation may include information such as cell ID and/or carrierfrequency, and/or the PRS information for the reference cell and/or theadditional or neighbor cells. Since PRS transmission may be theresponsibility of the eNB, the E-SMLC may obtain at least some of thePRS information from one or more eNBs where communication between anE-SMLC and an eNB may be via an LPPa interface or protocol.

According to an example embodiment, one or more transmission modes maybe provided and/or used in the communication system to transmit and/orreceive information, data, and/or signals. Table 3 illustrates exampleembodiments of transmission modes for a communication system (e.g., LTEand/or LTE-Advanced systems) that may be used to provide informationand/or signals disclosed herein. The transmission modes provided inTable 3 (e.g., except for TM-7, 8, and 9 in one embodiment) may use CRSfor both demodulation and measurement. Additionally, for TM-7 and 8shown in Table 3, DM-RS may be used for demodulation and CRS may be usedfor measurements. According to an embodiment, for TM-9 shown in Table 3,DM-RS and CSI-RS may be used for demodulation and measurement,respectively.

TABLE 3 Transmission modes in LTE/LTE-A Transmission mode (TM)Transmission scheme of PDSCH 1 Single-antenna port, port 0 2 Transmitdiversity 3 Transmit diversity if the associated rank indicator may be1, otherwise large delay CDD 4 Closed-loop spatial multiplexing 5Multi-user MIMO 6 Closed-loop spatial multiplexing with a singletransmission layer 7 If the number of PBCH antenna ports may be one,Single-antenna port, port 0; otherwise Transmit diversity 8 If the UEmay be configured without PMI/RI reporting: if the number of PBCHantenna ports may be one, single-antenna port, port 0; otherwisetransmit diversity If the UE may be configured with PMI/RI reporting:closed-loop spatial multiplexing 9 If the UE may be configured withoutPMI/RI reporting: if the number of PBCH antenna ports may be one,single-antenna port, port 0; otherwise transmit diversity Closed-loopspatial multiplexing with up to 8 layer transmission, ports 7-14

According to an example embodiment, channel state information (CSI)feedback may be provided and used. For example, multiple (e.g., two)types of reporting channels may be used such as PUCCH and/or PUSCH. ThePUCCH reporting channel may provide CSI feedback while allowing limitedfeedback overhead. The PUSCH reporting channel may allow a large amountof feedback overhead with less reliability. The PUCCH reporting channelmay be used for periodic CSI feedback for coarse link adaptation and/orthe PUSCH reporting may be triggered aperiodically for finer linkadaptation.

TABLE 4 Reporting modes in LTE/LTE-A Periodic CSI Aperiodic CSIreporting Scheduling Mode reporting channels channel Frequencynon-selective PUCCH Frequency selective PUCCH PUSCH

Downlink control channels may also be provided and/or used. The downlinkcontrol channels may occupy the first 1 to 3 OFDM symbol(s) in eachsubframe according to the overhead of the control channels. This dynamicresource allocation to handle downlink control channel overhead mayallow efficient downlink resource utilization, which may result inhigher system throughput. Various types of downlink control channels maybe transmitted within the downlink control channel region in eachsubframe, such as PCFICH (Physical Control Format Indicator Channel),PHICH (Physical Hybrid-ARQ Indicator Channel), and/or PDCCH (PhysicalDownlink Control Channel). The downlink control channel resource unitmay be defined as 4 contiguous REs in the frequency domain called REG(Resource Elements Group) as illustrated in FIGS. 9 and 10. FIG. 9illustrates an exemplary REG definition in downlink control channelregion with 2T× CRS. FIG. 10 illustrates an exemplary REG definition indownlink control channel region with 4T× CRS. As shown, if the CRS maybe located in the same OFDM symbol, the REG may be defined in 4contiguous REs without CRS.

In another embodiment, a physical control format indicator channel(PCFICH) may be provided and/or used as described herein. For example, aPCFICH may be transmitted in the 0^(th) OFDM symbol in each subframeand/or indicate the number of OFDM symbols used for downlink controlchannel in the subframe. The subframe-level dynamic downlink controlchannel resource allocation may be possible by using the PCFICH. A WTRUor UE may detect CFI (Control Format Indicator) from a PCFICH and thedownlink control channel region may be defined in the subframe accordingto the CFI value. Table 5 shows a CFI codeword which may be detectedfrom the PCFICH, and Table 6 shows details of downlink control channelresource allocation according to the CFI value, subframe type, andsystem bandwidth. In embodiments, The PCFICH may be skipped if asubframe may be defined as a non-PDSCH supportable subframe such that aWTRU or UE may not be trying to detect PCFICH in the subframe.

TABLE 5 CFI codeword CFI codeword CFI <b₀, b₁, . . . , b₃₁> 1 <0.1, 1.0,1, 1.0, 1, 1.0, 1, 1.0, 1, 1.0, 1, 1.0, 1, 1.0, 1, 1.0, 1.1, 0, 1.1, 0,1> 2 <1, 0.1, 1, 0.1, 1, 0.1, 1, 0.1, 1, 0.1, 1, 0.1, 1, 0, 1, 1.0, 1,1.0, 1, 1.0, 1, 1.0> 3 <1.1, 0, 1.1, 0, 1.1, 0, 1.1, 0, 1, 1, 0.1, 1,0.1, 1, 0.1, 1, 0.1, 1, 0.1, 1, 0.1, 1> 4 <0, 0.0, 0, 0.0, 0, 0.0, 0,0.0, 0, 0.0, 0, 0.0, 0, 0, 0, 0, 0, 0, 0, (Reserved) 0, 0, 0.0, 0, 0.0>

TABLE 6 Number of OFDM symbols used for PDCCH Number of Number of OFDMOFDM symbols for symbols for PDCCH when PDCCH when Subframe N_(RB)^(DL) >10 N_(RB) ^(DL) ≤10 Subframe 1 and 6 for frame structure 1, 2 2type 2 MBSFN subframes on a carrier 1, 2 2 supporting PDSCH, configuredwith 1 or 2 cell-specific antenna ports MBSFN subframes on a carrier 2 2supporting PDSCH, configured with 4 cell-specific antenna portsSubframes on a carrier not supporting 0 0 PDSCH Non-MBSFN subframes(except 1, 2, 3 2, 3 subframe 6 for frame structure type 2) configuredwith positioning reference signals All other cases 1, 2, 3 2, 3, 4

In an embodiment, four REGs may be used for PCFICH transmission in the0^(th) OFDM symbol in a subframe and/or the REGs may be uniformlydistributed in the whole system bandwidth to exploit frequency diversitygain. The starting point of PCFICH transmission may be differentaccording to the physical cell-ID (PCI) as illustrated in the FIG. 11.The frequency shift of PCFICH tied with cell-ID may provide theperformance of PCFICH detection performance by avoiding PCFICH collisionamong multiple neighbor cells while achieving diversity order four fromits distributed allocation. At a WTRU or UE receiver, a procedure (e.g.,a first procedure) for downlink control channel detection may bedecoding PCFICH to figure out the number of OFDM symbols in thesubframe. Given that downlink control resource may be defined by PCFICH,the PCFICH detection error may result in the loss of a downlink grant,an uplink grant, and/or PHICH reception.

A physical hybrid-ARQ indicator channel (PHICH) may be provided and/orused, as described herein. In an embodiment, a PHICH may be used totransmit an ACK or NACK corresponding to the PUSCH transmitted in anuplink subframe. A PHICH may be transmitted in a distributed manneracross system bandwidth and OFDM symbols within a downlink controlchannel. The number of OFDM symbols may be defined as PHICH duration andconfigurable via higher layer signaling. The PHICH resource position mayvary according to PHICH duration.

FIG. 12 shows exemplary PCFICH and PHICH resource allocations (e.g.,PCFICH and PHICH REGs allocation according to PCI). As shown in the FIG.12, multiple PHICH groups may be defined in a cell and a PHICH group maycomprise multiple PHICHs with orthogonal sequences and the PHICH for aWTRU or UE may be defined dynamically with resource information in anuplink grant such as lowest PRB index (l_(PRB_RA) ^(lowest_index)) andDM-RS cyclic shift (n_(DMRS)). Two index pairs (PHICH group index:n_(PHICH) ^(group), PHICH sequence index: n_(PHICH) ^(seq)) ) mayindicate the PHICH resource for a specific WTRU or UE. In the PHICHindex pair (n_(PHICH) ^(group), n_(PHICH) ^(seq)) each index may bedefined as follows:n _(PHICH) ^(group)=(l _(PRB_RA) ^(lowest_index) +n _(DMRS))mod N_(PHICH) ^(group)n _(PHICH) ^(seq)=(└l _(PRB_RA) ^(lowest_index) /N _(PHICH) ^(group) ┘+n_(DMRS))mod 2N _(SF) ^(PHICH)where the N_(PHICP) ^(group) may imply the number of PHICH groupsavailable in the system and may be defined as follows:

$N_{PHICH}^{group} = \{ \begin{matrix}\lceil {N_{g}( {N_{RB}^{DL}/8} )} \rceil \\{2 \cdot \lceil {N_{g}( {N_{RB}^{DL}/8} )} \rceil}\end{matrix} $where N_(g) may be a 2bit information transmitted via PBCH (PhysicalBroadcasting Channel) and the information may be within N_(g) ∈{⅙, ½, 1,2}.

Additionally, an orthogonal sequence according to the spreading factormay also be provided and/or used as illustrated, for example, in Table7.

TABLE 7 Orthogonal sequence according to sequence index and spreadingfactor. Orthogonal sequence Sequence index Normal cyclic prefix Extendedcyclic prefix n_(PHICH) ^(seq) N_(SF) ^(PHICH) = 4 N_(SF) ^(PHICH) = 2 0[+1 +1 +1 +1] [+1 +1] 1 [+1 −1 +1 −1] [+1 −1] 2 [+1 +1 −1 −1] [+j +j] 3[+1 −1 −1 +1] [+j −j] 4 [+j +j +j +j] — 5 [+j −j +j −j] — 6 [+j +j −j−j] — 7 [+j −j −j +j] —

A physical downlink control channel (PDCCH) may be provided and/or usedas described herein. For example, a PDCCH may be defined with one ormultiple consecutive CCE (Control Channel Element) resources in whichone CCE may comprise 9 REGs. The number of available CCE (N_(CCE)) maybe defined with N_(CCE)=└N_(REG)/9┘ where N_(REG) may be the number ofREGs not assigned to PCFICH or PHICH. Table 8-1 illustrates exemplaryavailable PDCCH formats by definition of a number of consecutive CCEsthat may be provided, used, and/or supported. As shown in the Table 8-1,the four PDCCH formats may be supported and/or the number of CCEsaccording to the PDCCH format may be different. The number of CCEs in aPDCCH format may be called an aggregation level.

TABLE 8-1 Supported PDCCH formats Number of PDCCH Number ofresource-element Number of format CCEs groups PDCCH bits 0 1 9 72 1 2 18144 2 4 36 288 3 8 72 576

In an embodiment, a WTRU or UE may monitor a PDCCH candidate and/orblindly decode the given number of times (e.g., as shown in the table8-2). The set of PDCCH candidates that may be monitored by a WTRU or UEmay be defined as a search space.

TABLE 8-2 PDCCH candidates monitored by a WTRU or UE Number of Searchspace S_(k) ^((L)) PDCCH Type Aggregation level L Size [in CCEs]candidates M^((L)) WTRU 1 6 6 or UE- 2 12 6 specific 4 8 2 8 16 2 Common4 16 4 8 16 2

Aggregation levels {1, 2, 4, 8} may be supported in a WTRU orUE-specific search space and the aggregation levels {4, 8} may besupported in common search space. The search space S_(k) ^((L)) ataggregation level L∈{1,2,4,8} may be defined by a set of PDCCHcandidates. For each serving cell on which PDCCH may be monitored, theCCEs corresponding to PDCCH candidate m of the search space S_(k) ^((L))may be given byL·{(Y_(k)+m′)mod└N_(CCE,k)/L┘}+iwhere Y_(k) may be defined as described herein and i=0, . . . , L−1. Forthe common search space, m′=m. Additionally, for the WTRU or UE specificsearch space and for the serving cell on which PDCCH may be monitored,if the monitoring WTRU or UE may be configured with carrier indicatorfield m′=m+M^((L))·n_(CI) where n_(CI) may be the carrier indicatorfield value. Otherwise, if the monitoring WTRU or UE may not beconfigured with a carrier indicator field, m′=m where m=0, . . . ,M^((L))−1 and M^((L)) may be the number of PDCCH candidates to monitorin the given search space. For the common search spaces, Y_(k) may beset to 0 for the two aggregation levels L=4 and L=8. For the WTRU orUE-specific search space S_(k) ^((L)) at aggregation level L, thevariable Y_(k) may be defined by Y_(k)=(A·Y_(k−1)) modD, whereY⁻¹=n_(RNTI)≠0, A=39827, D=65537 and k=└n_(s)/2┘, n_(s) may be the slotnumber within a radio frame.

As described herein PDCCHs may be enhanced (e.g., an ePDCCH may beprovided) by transmitting PDCCHs in a PDSCH region with a WTRU orUE-specific reference signal such that beamforming gain, frequencydomain ICIC, and/or PDCCH capacity improvement gain may be achievedand/or improved. FIG. 13 illustrates an exemplary ePDCCH multiplexingwith PDSCH (FDM multiplexing).

In an example embodiment, PUCCH may be allocated in relation to PDCCH.For example, the physical resources used for PUCCH may depend on one ormore parameters, such as N_(RB) ⁽²⁾ and/or N_(cs) ⁽¹⁾, given by higherlayers. The variable N_(RB) ⁽²⁾≥0 may denote the bandwidth in terms ofresource blocks that may be available for use by PUCCH formats 2/2a/2btransmission in each slot. The variable N_(cs) ⁽¹⁾ may denote the numberof cyclic shift used for PUCCH formats 1/1a/1bin a resource block usedfor a mix of formats 1/1a/1b and 2/2a/2b. The value of N_(cs) ⁽¹⁾ may bean integer multiple of Δ_(shift) ^(PUCCH) within the range of {0, 1 , .. . , 7}, where Δ_(shift) ^(PUCCH) may be provided by higher layers. Inan embodiment, there may be no mixed resource block present if N_(cs)⁽¹⁾=0. Additionally, there may be (e.g., at most) one resource block ineach slot supporting a mix of formats 1/1a/1b and 2/2a/2b. Resourcesthat may be used for transmission of PUCCH formats 1/1a/1b, 2/2a/2b and3 may be represented by the non-negative indices

$n_{PUCCH}^{({1,\overset{\sim}{p}})},{n_{PUCCH}^{({2,\overset{\sim}{p}})} < {{N_{RB}^{(2)}N_{sc}^{RB}} + {\lceil \frac{N_{cs}^{(1)}}{8} \rceil \cdot ( {N_{sc}^{RB} - N_{cs}^{(1)} - 2} )}}},{and}$$n_{PUCCH}^{({3,\overset{\sim}{p}})},$respectively.

Mapping to physical resources may be provided and/or used, for example,as described herein. In such embodiments, the block of complex-valuedsymbols z^(({tilde over (p)})) (i) may be multiplied with the amplitudescaling factor β_(PUCCH) to conform to a transmit power P_(PUCCH),and/or mapped in sequence starting with z^(({tilde over (p)})) (0) toresource elements. PUCCH may use one resource block in each of the twoslots in a subframe. Within the physical resource block used fortransmission, the mapping of z^(({tilde over (p)})) (i) two resourceelements (k, l) on antenna port _(p) and not used for transmission ofreference signals may be in increasing order of first k , then l and theslot number, and may start with the first slot in the subframe. Therelation between the index {tilde over (p)} and the antenna port numberp may be defined.

The physical resource blocks that may be used for transmission of PUCCHin slot n_(s) may be given by

$n_{PRB} = \{ \begin{matrix}\lfloor \frac{m}{2} \rfloor & {{{if}\mspace{14mu}( {m + {n_{s}\;{mod}\; 2}} ){mod}\; 2} = 0} \\{N_{RB}^{UL} - 1 - \lfloor \frac{m}{2} \rfloor} & {{{if}\mspace{14mu}( {m + {n_{s}\;{mod}\; 2}} ){mod}\; 2} = 1}\end{matrix} $where the variable m may depend on the PUCCH format. For formats 1, 1aand 1b

$\begin{matrix}{m = \{ \begin{matrix}N_{RB}^{(2)} & {{if}\mspace{14mu}\begin{matrix}{n_{PUCCH}^{({1,\overset{\sim}{p}})} <} \\{c \cdot {N_{cs}^{(1)}/\Delta_{shift}^{PUCCH}}}\end{matrix}} \\{\lfloor \frac{n_{PUCCH}^{({1,\overset{\sim}{p}})} - {c \cdot {N_{cs}^{(1)}/\Delta_{shift}^{PUCCH}}}}{c \cdot {N_{sc}^{RB}/\Delta_{shift}^{PUCCH}}} \rfloor + N_{RB}^{(2)} + \lceil \frac{N_{cs}^{(1)}}{8} \rceil} & {otherwise}\end{matrix} } & \; \\{\mspace{79mu}{c = \{ {\begin{matrix}3 & {{normal}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}} \\2 & {{extended}\mspace{14mu}{cyclic}\mspace{14mu}{prefix}}\end{matrix},} }} & \;\end{matrix}$for formats 2, 2a and 2b.m=└n _(PUCCH) ^((2,{tilde over (p)})) /N _(sc) ^(RB)┘,and for format 3m=└n _(PUCCH) ^((3,{tilde over (p)})) /N _(SF, 0) ^(PUCCH)┘.

Mapping of modulation symbols for the physical uplink control channelmay be illustrated in FIG. 14. In embodiments of simultaneoustransmission of sounding reference signal and PUCCH format 1, 1a, 1b or3 when there may be one serving cell configured, a shortened PUCCHformat may be used where the last SC-FDMA symbol in the second slot of asubframe may be left empty.

FDD HARQ-ACK procedures and/or methods for a configured serving cell maybe provided. For example, HARQ-ACK transmission on two antenna ports(p∈[P₀, P₁]) may be supported for PUCCH format 1a/1b. For FDD and oneconfigured serving cell, the WTRU or UE may use PUCCH resource n_(PUCCH)^((1,{tilde over (p)})) for transmission of HARQ-ACK in subframe n for{tilde over (p)} mapped to antenna port p for PUCCH format 1a/1b asdescribed herein below (e.g., where one or more of the following mayapply).

For a PDSCH transmission indicated by the detection of a correspondingPDCCH in subframe n−4, or for a PDCCH indicating downlink SPS release insubframe n−4 , the WTRU or UE may use n_(PUCCH) ^((1,{tilde over (p)}) ⁰⁾=n_(CCE)+N_(PUCCH) ⁽¹⁾ for antenna port p₀ in subframe n where n_(CCE)may be the number of the first CCE (e.g., lowest CCE index used toconstruct the PDCCH) used for transmission of the corresponding DCIassignment and/or N_(PUCCH) ⁽¹⁾ may configured by higher layers. For twoantenna port transmission the PUCCH resource for antenna port p₁ may begiven by n_(PUCCH) ^((1,{tilde over (p)}) ¹ ⁾=n_(CCE)+N_(PUCCH) ⁽¹⁾.

For a PDSCH transmission on the primary cell where there may not be acorresponding PDCCH detected in subframe n−4, the value of n_(PUCCH)^((1,{tilde over (p)})) may be determined according to higher layerconfiguration. For a WTRU or UE configured for two antenna porttransmission, a PUCCH resource value may map to two PUCCH resources withthe first PUCCH resource n_(PUCCH) ^((1,{tilde over (p)}) ⁰ ⁾ forantenna port p₀ and the second PUCCH resource n_(PUCCH)^((1,{tilde over (p)}) ¹ ⁾ for antenna port p₁. Otherwise, the PUCCHresource value may map to a single PUCCH resource n_(PUCCH)^((1,{tilde over (p)}) ⁰ ⁾ for antenna port p₀.

The FDD HARQ-ACK feedback procedures for more than one configuredserving cell may be based on a PUCCH format 1b with channel selectionHARQ-ACK procedure or a PUCCH format 3 HARQ-ACK procedures, for example.HARQ-ACK transmission on two antenna ports (p∈[p₀, p₁]) may be supportedfor PUCCH format 3.

For FDD with two configured serving cells and PUCCH format 1b withchannel selection, the WTRU or UE may transmit b(0)b(1) on PUCCHresource n_(PUCCH) ⁽¹⁾ selected from A PUCCH resources, n_(PUCCH,j) ⁽¹⁾where 0≤j≤A−1 and A∈{2,3,4}. HARQ-ACK(j) may denote the ACK/NACK/DTXresponse for a transport block or SPS release PDCCH associated withserving cell c, where the transport block and/or serving cell forHARQ-ACK(j) and A PUCCH resources may be given by a table.

A WTRU or UE configured with a transmission mode that may support up totwo transport blocks on serving cell, c, may use the same HARQ-ACKresponse for the transport blocks in response to a PDSCH transmissionwith a single transport block or a PDCCH indicating downlink SPS releaseassociated with the serving cell c.

Additionally, the WTRU or UE may determine the A PUCCH resources,n_(PUCCJ,j) ⁽¹⁾ associated with HARQ-ACK(j) where 0≤j≤A−1 according toone or more embodiments described herein (e.g., one or more of thefollowing example embodiments).

For a PDSCH transmission indicated by the detection of a correspondingPDCCH in subframe n−4 on the primary cell, or for a PDCCH indicatingdownlink SPS release in subframe n−4 on the primary cell, the PUCCHresource may be n_(PUCCH,j) ⁽¹⁾=n_(CCE)+N_(PUCCH) ⁽¹⁾, and fortransmission mode that supports up to two transport blocks, the PUCCHresource n_(PUCCH, j+1) ⁽¹⁾ may be given by n_(PUCCH, j+1)⁽¹⁾=n_(CCE)+1+N_(PUCCH) ⁽¹⁾ where n_(CCE) may be the number of the firstCCE used for transmission of the corresponding PDCCH and N_(PUCCH) ⁽¹⁾may be configured by higher layers.

For a PDSCH transmission on the primary cell where there may not be acorresponding PDCCH detected in subframe n−4 , the value of n_(PUCCH,j)⁽¹⁾ may be determined according to higher layer configuration. For atransmission mode that supports up to two transport blocks, the PUCCHresource n_(PUCCH, j+1) ⁽¹⁾ may be given by n_(PUCCH, j+1)⁽¹⁾=n_(PUCCH, j) ⁽¹⁾+1.

For a PDSCH transmission indicated by the detection of a correspondingPDCCH in subframe n−4 on the secondary cell, the value of n_(PUCCH, j)⁽¹⁾, and the value of n_(PUCCH, j+1) ⁽¹⁾ for the transmission mode thatsupports up to two transport blocks may be determined according tohigher layer configuration. The TPC field in the DCI format of thecorresponding PDCCH may be used to determine the PUCCH resource valuesfrom one of the resource values (e.g., four resource values) configuredby higher layers. For a WTRU or UE configured for a transmission modethat supports up to two transport blocks a PUCCH resource value may mapto multiple (e.g., two) PUCCH resources (n_(PUCCH, j) ⁽¹⁾,n_(PUCCH, j+1) ⁽¹⁾). Otherwise, the PUCCH resource value may map to asingle PUCCH resource n_(PUCCH, j) ⁽¹⁾.

Resource allocation in carrier aggregation situations may be provided.For ePDCCH transmission, localized and distributed resource allocationsmay be implemented for better support of UEs having different channelconditions in a cell. A localized resource allocation may allowfrequency selective gain so that an eNB scheduler may increase spectralefficiency by exploiting channel state information of a WTRU or UEexperiencing low Doppler frequency. A distributed resource allocationmay provide frequency diversity gain so that reliable PDCCH transmissionperformance may be achieved without channel state information, which maybe appropriate for a WTRU or UE suffering from high Doppler frequency.Currently, ePDCCHs may be designed based on single component carrierssuch that the performance may be limited if such designs may be used inmultiple carrier network.

In a system having multiple component carriers, the localized resourceallocation and distributed resource allocation may be optimized forfrequency selective scheduling gain and/or frequency diversity gain.Such ePDCCH designs may be focused on single component carrier such thatthe performance may be limited in a multiple carrier system.

Additionally, a WTRU or UE may provide a HARQ-ACK response in subframen+4 when a WTRU or UE receives PDSCH in subframe n. As the PDCCH blinddetection may desire or require some portion of time before startingPDSCH decoding, the PDSCH processing time may be reduced to less than 4ms. A timing advance may reduce PDSCH processing time so that a WTRU orUE may finish its decoding processing before n+4, for example, assuminga case in which a largest transport block size, highest rank, and/orlongest timing advance may be considered. That is, PDSCH processing timemay be further reduced. Since ePDCCH may be transmitted in a PDSCHregion, this may reduce PDSCH processing time, for example, in amultiple carrier system a maximum transport block size may be doubled. Asimilar processing time reduction may be observed for aperiodic CSIreporting. Aperiodic CSI reporting maybe triggered by a downlink controlchannel, the CSI feedback processing time may be reduced by ePDCCHreception and this may become more serious as the number of componentcarriers gets larger for CSI reporting at the same time. Unfortunately,as described, currently the PDSCH processing time and aperiodic CSIreporting processing time at a WTRU or UE receiver may be tighter due tothe use of ePDCCH instead of legacy PDCCH and currently these issues maybe more significant when carrier aggregation may be used.

Additionally, an uplink control channel allocation may be provided. Forexample, FDD HARQ-ACK feedback procedures may be based on a PUCCH format1a/1b (e.g., a dynamically assigned PUCCH format 1a/1b) for oneconfigured serving cell (e.g., in a single cell operation like Rel-8 orR8). For 2 or more DL serving cells for FDD, PUCCH feedback may use aPUCCH format 1b(e.g., a dynamically assigned PUCCH format 1b) withchannel selection (e.g., if 2 DL serving cells may be used) or a PUCCHformat 3(e.g., semi statically-configured PUCCH format 3) in combinationwith ARI (e.g., if 3 or more configured serving cell may be used). InTDD (e.g., Rel-10 TDD), single cell operation may be based on PUCCHformat 1(e.g., dynamically assigned PUCCH format 1) with channelselection. PUCCH format 1with channel selection (e.g., if 2 or more DLserving cells may be used) and/or PUCCH format 3or PUCCH F3 may be usedas a function of the RRC configuration.

In an embodiment, with a dynamically derived PUCCH resource, such as forthe case of single carrier operation or a DL assignment received on theprimary serving cell with DL carrier aggregation and for a PDSCHtransmission indicated by the detection of a corresponding PDCCH insubframe n−4 on the primary cell, and/or for a PDCCH indicating downlinkSPS release in subframe n−4 on the primary cell, the PUCCH resource maybe n_(PUCCH,j) ⁽¹⁾=n_(CCE)+N_(PUCCH) ⁽¹⁾, and/or for a transmission modethat supports up to two transport blocks, the PUCCH resourcen_(PUCCH,j+1) ⁽¹⁾ may be given by n_(PUCCH,j+1) ⁽¹⁾=n_(CCE)−1+N_(PUCCH)⁽¹⁾ where n_(CCE) may be the number of the first CCE used fortransmission of the corresponding PDCCH and N_(PUCCH) ⁽¹⁾ may beconfigured by higher layers. In an embodiment with PUCCH format 3, thePUCCH index maybe pre-configured through RRC and/or for a given DLsubframe n−4, the corresponding PUCCH index in UL subframe n may bederived from the ARI carried in the TPC field of the DL assignmentmessage on the SCell.

For a single carrier mode of operation, since the structure and/orresource region of the ePDCCH may be different from that of the legacyPDCCH, a PUCCH resource allocation mechanism may be specified to be ableto allocate PUCCH resources to users or UEs (or WTRUs) decoding DCI'susing ePDCCH, which may be difficult with multiple carriers.Additionally, for DL carrier aggregation, a PUCCH resource allocationmechanism may be used to allow users (or WTRUs) decoding ePDCCH on atleast one of the DL serving cells to transmit ACK/NACK informationcorresponding to the DL data transmissions scheduled on a primary andone or more secondary serving cells.

Frame Structure 2 TDD support may also be provided. In a TDD system, aPDSCH may be transmitted in a PDSCH region in a downlink subframe and/ora PDSCH region (e.g., DwPTS) in a subframe. In DwPTS (e.g., a DownlinkPilot Time Slot where a number of OFDM symbols reserved for downlinktransmission in a special subframe), the available number of OFDMsymbols for PDSCH transmission may be limited and/or vary according tothe configurations. Since the legacy PDCCH may be transmitted togetherin the same subframe, embodiments of ePDCCH transmission may be providedseparately.

If multiple component carriers may be configured with a different DL-ULsubframe configuration in a TDD system, the downlink control channel maynot be supported for a specific downlink subframe in a secondary cell,for example, when cross-carrier scheduling may be used. This may resultin a downlink subframe waste in the secondary cell. Due to the lack ofthe number of OFDM symbols in DwPTS and/or variable number of OFDMsymbols for PDSCH transmission, currently the ePDCCH transmission in asubframe may be needed (e.g., as described herein below) or detailedWTRU or UE behavior may be defined (e.g., as described herein below) tohelp avoid an error.

PDCCH fallback may be provided. For example, as ePDCCH may be supportedwith a legacy PDCCH in a network, a WTRU or UE may be configured to aspecific PDCCH type via higher layer signaling. In such an embodiment,there may be an ambiguity period in which an eNB scheduler may not knowwhether a WTRU or UE may monitor an RRC signaled PDCCH type or not. APDCCH fallback transmission, which may be received by a WTRU or UEregardless of the configured PDCCH type, may be defined to avoidresource waste and/or unexpected WTRU or UE behavior. In such anembodiment, if a WTRU or UE may be configurable between legacy PDCCH andePDCCH in a semi-static manner with higher layer signaling, a WTRU or UEmay need to be able to continuously or continually receive a PDCCHduring the configuration process.

Resource collision may further occur between PRS and ePDCCH. Forexample, when ePDCCH is used in a cell, PRS transmitted by the cell mayoverlap or collide with certain REs of the ePDCCH transmission. When thePRS BW overlaps the ePDCCH transmission BW, the PRS transmission maycollide with the DM-RS of the ePDCCH transmission. An example of thiscollision is shown in FIG. 15. As illustrated in FIG. 15, the Vshift mayequal 0. Such an overlap may result in performance degradation that,currently, may be too severe for the WTRU or UE to properly decode theePDCCH. The eNB may have no knowledge of which WTRUs or UEs may be awareof the PRS transmission, since the WTRU's or UE's support of OTDOA,performance of related measurements, and/or knowledge of PRS informationmay be based on the transparent communication between the WTRU or UE andthe E-SMLC, for example. Additionally, systems and/or methods may beprovided herein for handling and/or for avoiding such collisions.

As described herein, systems and/or methods may be provided to providean ePDCCH that may be used with multiple carriers. For example, aresource definition or description such as an ePDCCH resourceconfiguration may be provided. In the ePDCCH resource configuration, aresource element (RE) in a subframe may be used for ePDCCH that maysatisfy one or more of the following: may not collide with downlinkantenna ports (e.g., reference signal) from 0 to 22 except for antennaports {4, 5}; may not be occupied by PCFICH, PHICH, and/or PDCCH; notused for PSS/SSS and/or PBCH; may not be configured for a muted RE(e.g., zero-power CSI-RS, ABS, null RE); may not be used for PDSCH; maynot be used for PMCH for a configured MBFSN subframe(s); and/or whichmay be used for an above purpose, but may be differential by applyingmutually orthogonal patterns to both ePDCCH and non-ePDCCH (e.g., asdescribed herein).

A resource configured for FDD and TDD (e.g., in a single DL Carrier) mayalso be provided. For example, a subset of a physical resource block(s)(PRB), which may be referred to as a PRB-pair or RB, in a subframe maybe configured for an ePDCCH transmission and the ePDCCH resources may beprovided to a WTRU or UE by using broadcast channel(s) (e.g., MIB,SIB-x) and/or higher layer signalling (e.g., RRC, MAC, and the like).The subset of PRB may be consecutive PRBs or distributed PRBs. If asystem bandwidth may be 5 MHz (e.g. where 25 PRBs may be available,N_(RB) ^(max,DL)=25), the subset N_(RB) ^(ePDCCH) of PRBs for ePDCCH maybe configured, where N_(RB) ^(ePDCCH)<N_(RB) ^(max,DL). FIG. 16 shows anexample for ePDCCH multiplexing with PDSCH, where ePDCCH resources maybe allocated in a subframe. The PRB level ePDCCH multiplexing with PDSCHmay be used (e.g., as shown).

In an embodiment, ePDCCH PRBs may be reserved, for example, to enablesimpler ePDCCH reception and/or reduced blind decoding complexity.Additionally, the ePDCCH PRBs may be configured in PRB-pair level andmay include one or more of the following. For example, resourceallocation types for PDSCH transmission may be used including resourceallocation type 0, which may be a bitmap based indication with resourceblock group (RBG) where RBG may be defined according the systembandwidth; resource allocation type 1, which may be a bitmap basedindication with RBG subset; resource allocation type 2, which may be acontiguous resource allocation (e.g., starting RB number and/or lengthmay be given); the resource allocation type for ePDCCH resource may bedifferent according to ePDCCH modes (e.g., distributed and localizedtransmissions), for example, resource allocation type 0 may be used forlocalized transmission and resource allocation type 1 may be used fordistributed allocation; and/or the RBs for localized and distributedtransmission may be overlapped, that is, a PRB-pair may be used forlocalized and distributed transmission. Additionally, a per-PRB-pairlevel bitmap indication may be used where a bitmap per PRB-level may beprovided to indicate the ePDCCH resources that may use N_(DL,PRB) bitsand N_(DL,PRB) may indicate a number of PRB-pairs in the downlinksystem. In embodiments, predefined PRBs may also be used. For example,multiple PRB-pair subsets may be defined for ePDCCH and/or the subsetnumber may be informed to a WTRU or UE. Each PRB-pair subset may includeone or more numbers of PRB-pairs and the PRB-pairs in a PRB-pair subsetmay be mutually orthogonal with another PRB-pair subset. At least one ofPRB-pair subset may be used without configuration. The PRB-pair subsetmay be used for common search space, or used for the first PRB-pairsubset for WTRU or UE-specific search space. The subset number may beinformed to a WTRU or UE dynamically. For example, the subset number maybe indicated in each subframe in which a WTRU or UE may monitor orreceive ePDCCH. Predefined PRBs may be used for a common search space.Configuration based PRBs may be used for a WTRU or UE-specific searchspace. The ePDCCH PRB embodiments described herein may be used perePDCCH resource set if multiple ePDCCH resource sets may be configuredfor a WTRU or UE. The ePDCCH resource set and ePDCCH region may be usedinterchangeably.

According to an example embodiment, a WTRU or UE may have a particularbehavior to monitor ePDCCH based on a given ePDCCH indication. Forexample, the ePDCCH resources may be informed to a WTRU or UE viabroadcasting channels and/or RRC signaling. The WTRU or UE may monitorePDCCH within its search space which may be in a subset of PRBsconfigured for ePDCCH. The subset of PRBs may be informed to a WTRU orUE with dynamic indication in an implicit or explicit manner. Forexample, an indication bit may be transmitted in the subframe and/or aDM-RS scrambling sequence may indicate which subset of PRBs configuredfor ePDCCH may be used. The ePDCCH resources may be informed to a WTRUor UE with an ePDCCH resource index (ERI) from a set of ePDCCHconfigurations and/or the ERI may be informed via higher layer signalingor implicitly derived from at least one of following: a subframe indexand/or SFN; Cell-ID; and/or RNTI (e.g., C-RNTI, P-RNTI, SI-RNTI). A WTRUor UE may be informed regarding types of ePDCCH resources such as a“system ePDCCH resources” and/or a “WTRU or UE-specific ePDCCHresources.” WTRU or UE behavior associated with these ePDCCH resourcetypes may include one or more of the following: a WTRU or UE may receivethe system ePDCCH resource information via a broadcast channel or higherlayer signaling. A WTRU or UE may receive WTRU or UE-specific ePDCCHresource information from higher layer signaling. The WTRU orUE-specific ePDCCH resource may be the same as system ePDCCH resources.The WTRU or UE-specific ePDCCH resource may be a subset of system ePDCCHresources in a time and/or frequency domain. For example, a subset ofPRBs in a subframe and/or a subset of time subframe/frame may be theWTRU or UE-specific ePDCCH resources. In embodiments, a WTRU or UE maynot receive (e.g., may not assume to receive) PDSCH in a system ePDCCHresource that may not be in the WTRU or UE-specific ePDCCH resources. AWTRU or UE may receive (e.g., assume to receive) PDSCH in a systemePDCCH resources that may not be in the WTRU or UE-specific ePDCCHresources. A WTRU or UE may receive (e.g., may assume to receive) PDSCHin a WTRU or UE-specific ePDCCH resource if ePDCCH may not betransmitted in an ePDCCH PRB-pair.

According to an example embodiment, the ePDCCH PRBs may be configured inmultiple steps, such as long-term and short-term ePDCCH resources. Forexample, the long-term ePDCCH resources may be defined in a semi-staticmanner and/or the short-term ePDCCH resources may be defined within thelong-term ePDCCH resources in a dynamic manner. Also, the long-termePDCCH resources, cell-specific ePDCCH resources, semi-static ePDCCHresources, temporal ePDCCH resources, and/or higher layer configuredePDCCH resources may be used interchangeably.

In an embodiment, the long-term ePDCCH resource may be a set ofPRB-pairs within a system bandwidth. The resource allocation type 0, 1,or 2 may be used for indicating a set of PRB-pairs as a long-term ePDCCHresource. A number of bits (e.g., N_(RB) ^(max,DL)) may be used forbitmap based allocation to support flexibility (e.g., full flexibility).The resource indication for long-term ePDCCH resource may be informed toa WTRU or UE via broadcasting or higher layer signalling. A WTRU or UEmay know or assume that a part of long-term ePDCCH resources (e.g.,PRB-pairs) may be used for PDSCH transmission. If a PDSCH resourceallocation may collide with long-term ePDCCH resources while notcolliding with short-term ePDCCH resources, a WTRU or UE may know orassume that PDSCH may be transmitted in the resources. If a PDSCHresource allocation collides with both long-term and short-term ePDCCHresources, a WTRU or UE may assume that PDSCH may not be transmitted inthe resource and/or rate-match around the resources.

The short-term ePDCCH resource may be named as WTRU or UE-specificePDCCH resources, dynamic ePDCCH resources, per-subframe ePDCCHresources, and/or L1 signalling based ePDCCH resources. The short-termePDCCH resources may be a subset of long-term ePDCCH resources. Thesubset of ePDCCH resources may be indicated in each subframe so that theeNB may change the subset of ePDCCH resources from a subframe toanother.

The indication for short-term ePDCCH resources may be based on explicitsignalling. The explicit signalling may include one or multipleindication bits transmitted in the same subframe and/or the location ofthe indication bits may be fixed. According to an example embodiment,the fixed location may be the lowest index of the PRB-pairs configuredfor long-term ePDCCH resources. The fixed location may be predefinedirrespective of the long-term/short-term ePDCCH resources. For example,the lowest index of the PRB-pair in the system bandwidth. The fixedlocation may be based on distributed transmission.

The indication for short-term ePDCCH resources may be based on implicitsignalling. The implicit signalling may be a DM-RS in the PRB-pairsconfigured as short-term ePDCCH resources that may be scrambled with aspecific scrambling code which may be known to the eNB and/or the WTRUor UE. Therefore, a WTRU or UE may check the long-term ePDCCH resourceswith a specific scrambling code to figure out the short-term ePDCCHresources. Once the WTRU or UE finishes figuring out (e.g., determining)the short-term ePDCCH resources, WTRU or UE-specific search space may bedefined with the short-term ePDCCH resources. Therefore, the WTRU or UEmay monitors ePDCCHs within the WTRU or UE-specific search space. Theshort-term resource may be configured in a WTRU or UE-specific manner. AWTRU or UE may assume that PDSCH may not be transmitted in the PRB-pairconfigured for long-term ePDCCH resources, for example, even if thePRB-pairs may not be within short-term ePDCCH resources. The short-termresource may be configured in a cell-specific manner. A WTRU or UE mayreceive PDSCH in the PRB-pair configured for long-term ePDCCH resources,for example, if the PRB-pairs may not be within short-term ePDCCHresources.

Multiple ePDCCH resource sets may be provided or described herein and/ora subset of ePDCCH resource sets may be used in a subframe. The numberof ePDCCH resource sets may be configurable by eNB. The number of ePDCCHresource sets may be fixed irrespective of the system configuration. Asubset of ePDCCH resource set may be configured for a specific WTRU orUE as a WTRU or UE-specific search space. A subset of ePDCCH resourceset for a specific WTRU or UE may be predefined as a function of C-RNTIand/or subframe number. For example, if N_(ePDCCH) subsets of ePDCCHresource sets may be defined and one of the subsets of ePDCCH resourcesets may be configured to a specific WTRU or UE, the following equationmay be used to select which ePDCCH resource set may be used for the WTRUor UE. A subset of ePDCCH resource sets for a specific WTRU or UE may bedefined as k=n_(RNTI)modN_(ePDCCH) Table 8-3 shows an example of subsetconfigurations when four ePDCCH resource sets may be defined. In thetable, ‘v’ may indicate which set may be included in the subset.Additionally, k=n_(RNTI)mod3 may be used in Table 8-3.

TABLE 8-3 An example of multiple subsets of ePDCCH resource sets.Subset-k ePDCCH resource sets (Set-n) k = 0 k = 1 k = 2 Set-0 v v vSet-1 v — — Set-2 — v — Set-3 — — v

An ePDCCH resource set may include one or more PRB-pairs and/or thenumber of PRB-pairs per ePDCCH resource set may be fixed. For example,N_(set) PRB-pairs may be grouped as an ePDCCH resource set, where theN_(set) PRB-pairs may be consecutive or distributed over the systembandwidth.

Additionally, an ePDCCH resource set may be configured as a localizedePDCCH resource or a distributed ePDCCH resource. If an ePDCCH resourceset may be defined as localized ePDCCH resource, eCCEs within the ePDCCHresource set may be defined as localized ePDCCH transmission (LeCCE). Inone ePDCCH resource set, multiple LeCCEs may be defined. The REs for aLeCCE may be located within a PRB-pair. If an ePDCCH resource set may bedefined as distributed ePDCCH resource, eCCEs within the ePDCCH resourceset may be defined as distributed ePDCCH transmission (DeCCE). In anePDCCH resource set, multiple DeCCEs may be defined. The REs for a DeCCEmay be located over two or more number of PRB-pair. A DeCCE may includemultiple eREGs, where an eREG may include multiple REs within aPRB-pair. The multiple eREGs for a DeCCE may be transmitted overmultiple PRB-pairs within an ePDCCH resource set. The first ePDCCHresource set may be predefined as distributed ePDCCH resource and/or theother ePDCCH resource sets may be configured as one of localized anddistributed ePDCCH resource.

The number of PRB-pairs per ePDCCH resource set may vary according tothe system parameters. For example, the number of PRB-pairs per ePDCCHresource set may be defined as a function of the system bandwidth or thenumber of RBs (e.g., N_(RB) ^(DL)) such as N_(set)=f(N_(RB) ^(DL)) . Inthis case, one or more of the following may apply:

N_(set) = f(N_(RB)^(DL)) = ⌈N_(RB)^(DL)/N_(s)⌉,where N_(s) may be a fixed number or eNB configured number; the functionfor the number of PRB-pairs per set may be different according to theePDCCH transmissions such as localized and distributed ePDCCH; and/or alookup table may be defined for N_(set) according to N_(RB) ^(max,DL).The value of N_(set) may be different from the Table 8-4 shown below.

TABLE 8-4 Number of PRB-pair (N_(set)) according to the systembandwidth. System Bandwidth (N_(RB) ^(max,DL)) N_(set) ≤10 2 11-26 427-63 6  64-110 8

In an embodiment, the fixed value of N_(set) may be used for commonsearch space, while multiple value of N_(set) may be used for WTRU orUE-specific search space. The multiple value of N_(set) for WTRU orUE-specific search space may be changed according to at least one of thesystem bandwidth, the subframe number and/or SFN number, and/or aconfigured parameter via broadcasting or higher layer signalling.

Among the multiple ePDCCH resource sets, a subset may also be selectedexplicitly (e.g., using one or more indication bit(s)). For example, oneor more indication bit(s) may be transmitted in the PDCCH region in thesame subframe. In this embodiment, at least one of a PCFICH in the PDCCHregion or a DCI may be transmitted for indication bit transmission. ThePCFICH in the PDCCH region may be used to indicate how many ePDCCHresource sets may be used. In this case, the number of OFDM symbols forthe PDCCH may be defined as either following the same number indicatedin PCFICH or configured via higher layer signalling. The DCI may bedefined and/or transmitted in a common search space. The DCI may includeat least one of a number of ePDCCH resource sets and/or a resourceallocation index.

The one or more indication bit(s) may be transmitted in the same orprevious subframe in the PDSCH region. In this case, an indicationchannel may be transmitted for indication transmission. The indicationchannel (e.g., ePCFICH) may be defined and/or transmitted in a specificlocation. The location for the indication channel may be a zero-powerCSI-RS or a subset REs of zero-power CSI-RS. If zero-power CSI-RSlocation may be used, the subset of ePDCCH resource sets may be validwithin the duty cycle. The indication channel may be defined in thefirst ePDCCH resource set. The indication channel may be transmittedover N_(set) PRB-pairs, for example, when N_(set) PRB-pairs may be usedfor the first ePDCCH resource set. The indication channel may be definedin the fixed location in the subframe and/or the location may be changedaccording to the cell-ID and/or subframe number. The indication channelmay be transmitted in the subframe n−1 and/or the indication informationmay be applied in the subframe n.

Among the multiple ePDCCH resource sets, a subset may be selectedimplicitly. For example, a specific DM-RS scrambling sequence may beused for the subset of ePDCCH resource sets used for ePDCCH transmissionin the subframe. A WTRU or UE may detect the ePDCCH resource sets usedfor ePDCCH transmission in the subframe, for example, by using thesequence scrambled to the DM-RS. Once a WTRU or UE finishes the ePDCCHresource set detection, the WTRU or UE may figure out the WTRU orUE-specific search space. The WTRU or UE may start blind detectionwithin the WTRU or UE-specific search space.

Multiple ePDCCH resource sets, which may be interchangeably used asePDCCH region, ePDCCH PRB set, and/or ePDCCH set, may be implemented.Each ePDCCH resource set may include a non-overlapped N_(set) PRB-pairwhere the N_(set) may have one or more values. In this embodiment, eachePDCCH resource set may be configured as ePDCCH localized transmissionor ePDCCH distributed transmission. The N_(set) may also, oralternatively, be configured via higher layer signalling, predefined asa function of system parameter(s), and/or defined as a combination ofsystem parameters ad higher layer signalling.

A K_(set) ePDCCH resource set may also be configured for a WTRU or UEwhere the K_(set) may have two or more values. In this embodiment, theN_(set) for each ePDCCH resource set may be used independently whenK_(set) ePDCCH resource sets may be configured, the K_(set) may beconfigured via higher layer signalling, the K_(set) may be indicated inbroadcasting channel (e.g., MIB, SIB-x), and/or the K_(set) may bedifferent according to the SFN/subframe index.

When the N_(set) for each ePDCCH resource set may be used independently,one or more of the following may apply: the N_(set) may be larger forlocalized transmission so that frequency selective scheduling gain maybe increased while the reasonable resource utilization may be provided;the N_(set) may be larger for distributed transmission so that frequencydiversity gain may be maximized; the N_(set) may be defined as afunction of the system bandwidth or other cell-specific parameters forat least one of ePDCCH transmissions (e.g., localized and distributedtransmission), for example, the N_(set) may be predefined for localizedtransmission according to the system bandwidth while N_(set) may beconfigured for distributed transmission via higher layer signalling;and/or two N_(set) may be configured such as N_(set, 1), and N_(set, 2)if K_(set) may be larger than 1, and the N_(set, 1) may be used for theconfigured ePDCCH resource set(s) as a distributed transmission whileN_(set, 2) may be used for all configured ePDCCH resource set(s) as alocalized transmission.

The K_(set) ePDCCH resource set may be configured as a single ePDCCHresource set or multiple ePDCCH resource sets. If a WTRU or UE may beconfigured with the multiple ePDCCH resource sets, the WTRU or UE mayassume that K_(set)=2. In this embodiment, if a WTRU or UE may beconfigured with a single ePDCCH resource set, the ePDCCH resource setmay be configured as localized or distributed ePDCCH transmission and/orthe WTRU or UE may assume that the ePDCCH resource set may be configuredas distributed transmission. If a WTRU or UE may be configured withmultiple ePDCCH resource sets, at least one of ePDCCH resource set maybe configured as distributed ePDCCH transmission; an ePDCCH resource setmay be defined as primary ePDCCH resource set and the other ePDCCHresource set may be defined as secondary ePDCCH resource set; and/or theN_(set) may be different according to the ePDCCH resource set. Forexample, the first set may have N_(set)=4 and the second set may haveN_(set)=2.

In an embodiment, the ePDCCH resources may be configured and/or defineddifferently according to or based on the ePDCCH search space. Forexample, the ePDCCH common search space may be configured in acell-specific manner and the WTRU or UE-specific search space may beconfigured in a WTRU or UE-specific manner.

The ePDCCH common search space resource may be configured via at leastone of the following. In one embodiment, a minimum set of PRB pairs maybe configured in a specific time and/or frequency location in apredefined manner. For example, 4 PRB-pairs or 6 PRB-pairs may bedefined as a minimum set of PRB pairs for the common search space andthe center 4 or 6 PRB-pairs in the downlink system bandwidth may be usedfor common search space.

Additionally, in a subframe including PSS/SSS and/or PBCH, the locationof ePDCCH common search space may be located next to the center 6PRB-pairs if the downlink system bandwidth may be larger than 6PRB-pairs. In this embodiment, the 4 or 6 PRB-pairs may be equallydivided and located in both sides of center 6 PRB-pairs.

The PRB pairs for the common search space may also be extended in a WTRUor UE-specific manner. In this embodiment, the minimum set of PRB pairsmay be considered as the first ePDCCH common search space set and theWTRU or UE-specific common search space extension may be considered asthe second EPDCCH common search space set. As such, two ePDCCH commonsearch space sets may be configured and one of them may be configured ina cell-specific manner and the other may be configured in a WTRU orUE-specific manner. In such an embodiment, a subset of DCI formats thatmay be monitored in the common search space may be monitored in acell-specific common search space and the others may be monitored in aWTRU or UE-specific common search space. For example, DCI formats1A/1B/1C may be monitored in the cell-specific common search space andDCI formats 3/3A may be monitored in the WTRU or UE-specific commonsearch space. Additionally, the WTRU or UE-specific common search spacemay be configured via higher layer signalling or signaled in abroadcasting channel. Furthermore, in an embodiment, two common searchspace resource sets may be configured and the first ePDCCH common searchspace resource set may be predefined in a fixed location while thesecond ePDCCH common search space resource set may be configured viabroadcasting channels such as MIB or SIB-x.

The WTRU or UE-specific search space may be configured via at least oneof the following. In an embodiment, a WTRU or UE-specific ePDCCHresource set may be defined as a set of a number of PRBs. For example,one of the {2, 4, 8} PRBs may be configured for a WTRU or UE-specificePDCCH resource set via higher layer signalling. Additionally, a bitmapmay be used to indicate the PRB-pairs configured for common searchspace. In an embodiment, up to two WTRU or UE-specific ePDCCH resourcesets may be configured per WTRU or UE and the two WTRU or UE-specificePDCCH resource sets may be overlapped partially or fully in PRB pairs.

Furthermore, the PRB pairs for a WTRU or UE-specific search space andthe PRB pairs for a common search space may be overlapped. In thisembodiment, one or more of following may apply. The second ePDCCH commonsearch space resource set may be overlapped with a WTRU or UE-specificePDCCH resource set where, for example, the second ePDCCH common searchspace set may be either a WTRU or UE-specific common search space or acell-specific common search space. If two ePDCCH common search spaceresource sets may be configured, the two EPDCCH common search spaceresource sets may be fully or partially overlapped with each other.

Embodiments may be described herein for resource configuration for TDDin the embodiment of a single DL carrier. In frame structure 2, severalUL-DL subframe configurations and associated HARQ-ACK and UL/DL grantmay be defined, for example, in order to fully utilize UL/DL resources.Table 9 shows an exemplary UL-DL subframe configuration that may allowvarious uplink downlink traffic asymmetries according to the networkenvironments.

TABLE 9 UL-DL subframe configuration Uplink- Downlink- downlinkto-Uplink config- Switch-point Subframe number uration periodicity 0 1 23 4 5 6 7 8 9 0 5 ms D S U U U D S U U U 1 5 ms D S U U D D S U U D 2 5ms D S U D D D S U D D 3 10 ms  D S U U U D D D D D 4 10 ms  D S U U D DD D D D 5 10 ms  D S U D D D D D D D 6 5 ms D S U U U D S U U D

In Table 9, ‘D’ and ‘U’ denote downlink subframe and uplink subframe,respectively. ‘S’ denotes special subframe that may be used when thesubframe configuration may be changed from downlink to uplink, e.g., asa guard time so that a WTRU or UE may prepare to transmit signals. Thespecial subframe may comprise DwPTS, UpPTS, and GP where DwPTS and UpPTSperiods may be a number of OFDM symbols for downlink and uplinktransmissions, respectively. The rest of the times except for DwPTS andUpPTS may be considered as GP. Table 10 shows example special subframeconfigurations.

TABLE 10 Configuration of special subframe in normal CP (lengths ofDwPTS/GP/UpPTS) Normal cyclic prefix in downlink UpPTS Normal SpecialDwPTS cyclic subframe # of DL OFDM # of SC-FDMA prefix configurationsymbols symbols in uplink 0 3  6592 · T_(s) 1 2192 · T_(s) 1 9 19760 ·T_(s) 2 10 21952 · T_(s) 3 11 24144 · T_(s) 4 12 26336 · T_(s) 5 3  6592· T_(s) 2 4384 · T_(s) 6 9 19760 · T_(s) 7 10 21952 · T_(s) 8 11 24144 ·T_(s)

Since an ePDCCH may be transmitted based on antenna ports 7˜10, theePDCCH may not be transmitted in a special subframe configuration. Insuch a case, a WTRU or UE behavior for PDCCH reception may be providedas described herein. For example, a WTRU or UE may assume that theePDCCH may be limited to transmission in a normal downlink subframe. AWTRU or UE may assume that downlink control channel may be transmittedvia legacy PDCCH in a special subframe irrespective of the PDCCHconfiguration. A WTRU or UE may assume to receive ePDCCH targetingspecial subframe n in downlink subframe n-k where k may be definedaccording to the UL-DL subframe configuration and k may be defined asthe downlink subframe closest to the subframe n. If a WTRU or UE may beconfigured to receive ePDCCH, the WTRU or UE may skip blind decoding ofePDCCH in the special subframe. ePDCCH and legacy PDCCH reception may beconfigurable, for example, as shown in the exemplary TDD UL-DL subframeconfiguration in Table 11 where ‘E’ and ‘L’ denote ePDCCH and legacyPDCCH, respectively.

TABLE 11 legacy PDCCH (L)-ePDCCH (E) subframe configuration LegacyPDCCH- Downlink- ePDCCH to-Uplink config- Switch-point Subframe numberuration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms E L — — — E L — — — 1 5ms E E — — — E E — — — 2 5 ms E L — — E E L — — E 3 5 ms E E — — E E E —— E 4 5 ms E L — E E E L — E E 5 5 ms E E — E E E E — E E 6 10 ms  E L —— — E E E E E 7 10 ms  E E — — — E E E E E 8 10 ms  E L — — E E E E E E9 10 ms  E E — — E E E E E E 10 10 ms  E L — E E E E E E E 11 10 ms  E E— E E E E E E E 12 5 ms E L — — — E L — — E 13 5 ms E E — — — E E — — E14 Reserved 15 Reserved

A WTRU or UE may assume that ePDCCH may or may not be transmitted and/ormonitored in a specific special subframe based on one or more of thefollowing. In a downlink normal cyclic prefix (CP) case, ePDCCH may betransmitted and/or monitored in the special subframe configuration {1,2, 3, 4, 6, 7, 8} in Table 10 (e.g., and may not be transmitted and/ormonitored in configurations 0 and 5, for example, for such TDD and/ordownlink normal CP). The special subframe configuration in which ePDCCHmay be transmitted may be predefined as other than {1, 2, 3, 4, 6, 7,8}. For example, ePDCCH may be transmitted and/or monitored in a DwPTScomprising more than m OFDM symbols, where m may be 3, 8, 9, or 10.Additionally, if a special subframe configuration 0 or 5 may be used ina cell, a WTRU or UE behavior for PDCCH reception may be defined in oneor more of the following ways: a WTRU or UE may assume that ePDCCH maynot be transmitted and/or monitored in a special subframe (e.g., 0 or 5which may not be included in the special subframe configuration {1, 2,3, 4, 6, 7, 8} described above), otherwise, a WTRU or UE may monitorePDCCH in a special subframe; a WTRU or UE may assume that ePDCCHtargeting the special subframe n may be transmitted in subframe n-k,where k may be defined as the downlink subframe closest to the subframen; a WTRU or UE may assume that PDCCH may be transmitted via legacyPDCCH in the special subframes; and/or a WTRU or UE may follow theconfiguration of ePDCCH and legacy PDCCH which may be predefined. If aspecial subframe configuration other than 0 and 5 may be used in a cell,a WTRU or UE may assume that ePDCCH may be transmitted in DwPTS. Theremay be a special subframe in which DwPTS may be equal to or longer thanN_(DWPTS) [OFDM symbol]. The N_(DwPTS) may be configured by higherlayers. The N_(DwPTS) may be fixed as 9 (e.g., which may be equivalentto 19760·T_(s) for normal CP and 20480·T_(s) for extended CP).

If multiple component carriers may be configured in TDD mode, eachcomponent carrier may have a different UL-DL subframe configuration. Forexample, PCell and SCell may be configured with UL-DL configuration 1and 2, respectively, as shown in the FIG. 17. FIG. 17 illustrates anexample embodiment of carrier aggregation with different TDD UL-DLconfiguration. In such a case, a downlink subframe for PCell may not beavailable in subframes 3 and 8, although a WTRU or UE may expect toreceive PDSCH in SCell, which may result in scheduling restriction ifcross carrier scheduling may be activated since a WTRU or UE may receivePDCCH in PCell. At least one of WTRU or UE behaviors described hereinmay be used when a cross carrier scheduling may be activated, which mayresolve such issues. For example, a WTRU or UE may assume that the PDCCHmay be transmitted in SCell if a normal downlink subframe may not beavailable in PCell in an SCell downlink subframe. A WTRU or UE maymonitor ePDCCH in SCell for PDCCH reception regardless of the PDCCHconfiguration. A WTRU or UE may monitor the legacy PDCCH if the WTRU orUE may be configured to receive the legacy PDCCH in PCell. A WTRU or UEmay monitor the legacy PDCCH or ePDCCH according to a subframe with apredefined PDCCH reception configuration. A WTRU or UE may assume thatthe PDCCH may be transmitted in SCell if a normal downlink subframe orspecial subframe may not available in PCell in an SCell downlinksubframe. A WTRU or UE may continue to monitor PDCCH in a specialsubframe if the special subframe configuration may not be 0 or 5. If aspecial subframe configuration 0 or 5 may be used, a WTRU or UE mayassume that PDCCH may be transmitted in SCell. If multiple SCells may beconfigured, the SCell locating lowest frequency may be considered asPCell for PDCCH reception.

Resource allocation (e.g., ePDCCH resource allocation) in a multiplecarrier system (e.g. in multiple DL carriers) may be disclosed,provided, and/or used. In a multiple carrier system, the resources forePDCCH may be defined in a PDSCH region and the ePDCCH resources may bemultiplexed with PDSCH in an FDM manner. The ePDCCH resource may beconfigured in one or more of the following ways.

ePDCCH resources may be limited to configuration in the Primary cell(PCell) if cross-carrier scheduling may be activated. In such a case, aWTRU or UE may assume that an ePDCCH may be limited to transmission inPCell and the WTRU or UE may limit monitoring for ePDCCH reception toPcell. ePDCCH resources may not be allowed in a Secondary cell (SCell).Additionally, ePDCCH resources in SCell may be considered as muted RBsfrom a WTRU or UE perspective such that the WTRU or UE rate-matches theRBs if a PDSCH may be scheduled in the RBs.

Additionally, ePDCCH resources may be configured in a single cell ifcross-carrier scheduling may be activated. The cell (e.g., componentcarrier) that has ePDCCH resources may be configured by higher layersignalling. The cell (e.g., component carrier) that has ePDCCH resourcesmay be predefined. For example, a broadcast channel (e.g., SIB-x) mayindicate the cell. The component carrier that has the ePDCCH may befixed or changed according to subframe and/or radio frame. If thecomponent carrier having the ePDCCH may be changed, a WTRU or UE mayimplicitly derive which component carrier has the ePDCCH in a specificsubframe and/or radio frame by using an SFN number.

ePDCCH resources may be defined in a subset of component carriers whichmay be equal to or smaller than the configured component carriers for aspecific WTRU or UE. The subset of component carriers may be configuredby higher layers. Additionally, the subset of component carriers may bepredefined including, for example, component carrier number and centerfrequency. The subset of component carriers may also be dynamicallychanged from a subframe to another. The subset pattern may be predefinedand/or tied with an SFN number.

In an embodiment, ePDCCH and legacy PDCCH may be configured at the sametime. In such an embodiment, a subset of component carriers may beconfigured for ePDCCH while the other component carriers may beconfigured for legacy PDCCH. Therefore, a WTRU or UE may monitor theePDCCH in the component carriers configured for ePDCCH and the legacyPDCCH in the other component carriers.

An ePDCCH frequency diversity mode may be interchangeably defined andmay not be limited to ePDCCH distributed transmission, ePDCCH frequencydiversity scheme, ePDCCH distributed mode, and/or Mode-1. For an ePDCCHfrequency diversity mode (e.g., distributed mode, Mode-1, etc.), theresources for an ePDCCH may be distributed across system frequencybandwidth to achieve frequency diversity gain. The ePDCCH resource forfrequency diversity mode may be configured as described herein. Forexample, enhanced Control Channel Elements (eCCEs) and/or enhancedResource Group Elements (eREGs) may be distributed to multiple downlinkcarriers (e.g., DL cells), where an ePDCCH may be transmitted by using{1, 2, 4, or 8} eCCEs and an eCCE may comprise N_(eREGs). The size-N maybe predefined. If a cross carrier scheduling may be activated, an ePDCCHmay be distributed over the PCell, and an ePDCCH may be otherwisedistributed across multiple component carriers (e.g., DL carrier). ForeCCE aggregation, a WTRU or UE may aggregate eCCEs across multiplecomponent carriers (e.g., DL carrier), as shown in FIG. 18 for instance.FIG. 18 illustrates an exemplary eCCE aggregation across multiplecarriers in distributed resource allocation. For eCCE-to-eREG mapping,eREGs may be distributed across multiple carriers. ePDCCH Mode-1 may beconfigured within center 5 MHz (e.g., 25 PRBs) bandwidth.

The ePDCCH frequency selective mode may be interchangeably defined andnot limited to ePDCCH localized transmission, ePDCCH frequency selectivescheme, ePDCCH localized mode, and/or Mode-2. For ePDCCH frequencyselective mode (e.g., localized mode, Mode-2, and the like), theresources for an ePDCCH may be located in one or two RBs according tothe eCCE aggregation level to achieve frequency selection gain. TheePDCCH resource for frequency selective mode may be configured asdescribed herein. For example, eCCEs may be located within the samePRB-pairs if multiple eCCEs may be aggregated. eREGs located within asame PRB-pair and/or neighbor PRB-pairs may be aggregated to form aneCCE. ePDCCH Mode-2 may be configured within center 5 MHz (e.g., 25PRBs) bandwidth.

In a multiple component carrier system, the ePDCCH Mode-1 (e.g., ePDCCHfrequency diversity mode) and/or the ePDCCH Mode-2 (e.g., ePDCCHfrequency selective mode) may be configured as described herein. Forexample, a WTRU or UE may monitor ePDCCH Mode-2 in PCell and ePDCCHMode-1 in other configured cells if cross-carrier scheduling may not beactivated. A WTRU or UE may monitor ePDCCH Mode-1 and/or ePDCCH Mode-2in PCell if cross-carrier scheduling may be activated. A subset ofePDCCH Mode-1 and/or ePDCCH Mode-2 resources may be defined as ePDCCHMode-3 which may span to multiple PRBs in center frequency bandwidth.

An ePDCCH resource set may be defined within a cell such that theN_(set) PRB-pairs for an ePDCCH resource set may be located within acell. For example, the K_(set) ePDCCH resource sets may also be locatedwithin a cell. As such, N_(set) and/or K_(set) may be defined per cellwhen multiple component carriers may be used. The cell may also beinterchangeably used as component carrier, PCell, or SCell. In thiscase, at least one set among K_(set) in the PCell may be defined asePDCCH distributed transmission and/or K_(set) may be defined as ePDCCHlocalized transmission or ePDCCH distributed transmission in an SCell.

Additionally, an ePDCCH resource set may be defined over multiplecomponent carriers so that the N_(set) PRB-pairs for an ePDCCH resourceset may be located over multiple component carriers. In this case, whenan ePDCCH resource set may be configured as distributed transmission,the N_(set) PRB-pairs for an ePDCCH resource set may be located overmultiple component carriers; and/or if an ePDCCH resource set may beconfigured as localized transmission, the N_(set) PRB-pairs for theePDCCH resource set may be located in the same cell.

An enhanced resource element group (eREG) may also be provided asdescribed herein. A minimum resource unit for ePDCCH may be definedand/or called eREG (enhanced Resource Element Group). An eREG may beformed with a fixed number of REs. An eREG that may be formed with avariable number of REs where the number of REs may be differentaccording to at least one of following factors: an eREG number; subframenumber and/or subframe type (e.g., MBSFN subframe), CSI-RS configurationincluding zero-power CSI-RS; a PRS configuration; an existence ofSSS/PSS and PBCH; and/or the like. An eREG may be formed with availableREs in a given time/frequency resource grid such as N×M REs in PDSCHregion not including one or more (e.g., each of or a subset) offollowing: zero-power CSI-RS and non-zero-power CSI-RS, SSS/PSS and/orPBCH, PRS, DM-RS, CRS, ePHICH, ePCFICH, and/or the like.

A time and/or frequency resource grid in PDSCH region (N×M REs) for eREGmay be provided and defined in at least one of following manners: N andM indicates frequency and time RE granularity, respectively; N may be afixed number between 1 and 12 (in an embodiment an exemplary fixednumber for N may be one or two); N may be configurable by Broadcasting(e.g., MIB or SIB-x) and/or RRC configuration; N may be different in asubframe for localized transmission (ePDCCH Mode-1) and distributedtransmission (ePDCCH Mode-2) (e.g., a small number of N may be used fordistributed transmission (N_(dist)) and/or a large number of N maybeused for localized transmission (N_(local)) where N_(local)>N_(dist)); Mmay be defined as 14-N_(PDCH) in normal CP and 12-N_(PDCCH) in extendedCP, where NPDCCH may denote a number of OFDM symbols used for legacyPDCCH and indicated by PCFICH in the subframe; M maybe be defined asfixed number, such as 11 in normal CP and 9 in extended CP; M may beconfigurable by broadcasting (e.g., MIB or SIB-x) and/or RRCconfiguration; M may be different in a subframe for localizedtransmission (ePDCCH Mode-1) and distributed transmission (ePDCCHMode-2) (e.g., a small number of M may be used for distributedtransmission (M_(dist)) and a large number of M may be used forlocalized transmission (M_(local)) where M_(local)>M_(dist)).

In an embodiment, an eREG may be formed with a fixed or variable numberof REGs where REG may be defined as four contiguous REs in PDSCH regionnot used for other purposes, but for ePDCCH as disclosed herein. Forexample, one eREG may include nine REGs, and by doing so, an eREG may besimilar to a CCE (e.g., which may simplify the standardization evolutionof terminology from PDCCH used).

FIG. 19 shows an example embodiment of an eREG definition. For example,FIG. 19 illustrates a PRB-pair that may be used for ePDCCH transmissionaccording to the number of antenna ports (e.g., ports 7-10 in leftportion of FIG. 19 and port 7-8 in right portion of FIG. 19). As shownin FIG. 19, N=1 and M=11 may be used in a subframe not including CSI-RSand PSS/SSS. An eREG may span to both slots in a PRB-pair and the numberof REs for eREGs may be different according to the eREG number due tothe CRS and DM-RS. For example, the eREG #n may include 3 REs while eREG#n+2 may include 11 REs (e.g., as shown in the left portion of FIG. 19)according to the existence of DM-RS and CRS. Also, fully FDM based eREGmultiplexing may be used in order to utilize the power for unused eREGsflexibly. As an example, if eREG #n+7 may not be used the power may bereused to boost up eREG n+2 power.

In an embodiment, an eREG resource may be defined in an interleavedmanner to randomize the RE location so that the channel estimationperformance may be equalized regardless of the eREG number. Therefore, aWTRU or UE may receive an eREG based on the virtual eREG to physicaleREG mapping rule.

A fixed number of eREG may be defined per PRB-pair configured as anePDCCH resource. For example, 16 eREGs may be defined per PRB-pair,irrespective of the configuration of reference signal, subframe type, CPlength, etc. The eREG may be defined in an interlaced manner so that theREs except in a PRB-pair may be cyclically allocated for the eREG 0˜15in a frequency first manner. When 16 eREGs may be available perPRB-pair, 16×N_(set) eREGs may be available for an ePDCCH resource sethaving N_(set) PRB-pairs.

In an embodiment, eREG subset blocking may be used so that a subset ofeREGs in an ePDCCH resource set may be blocked and not used to form aneCCE. This may enable improved or better inter-cell interferencecoordination, since non-overlapped eREGs may be used between neighborcells.

For the eREG subset blocking, a subset of eREGs among 16×N_(set) may beindicated via higher layer signalling and the subset may not be countedas an eREG. Therefore, physical eREGs and virtual eREGs may be defined.The virtual eREGs may be used to form an eCCE. Therefore, the number ofphysical eREGs may be equal to or smaller than that of virtual eREGs.The subset of eREGs may be predefined as a form of eCCE, PRB-pair,and/or ePDCCH resource set. Thus, the indication may be based on theeCCE number, PRB-pair number, and/or ePDCCH resource set number. Thesubset of eREGs may be predefined as a table so that an index maycorrespond to a subset of eREGs. A bitmap may be used to indicate thesubset of eREG which may be blocked.

The subset of eREGs for blocking may be defined as a function of one ormore system parameters such as PCI, SFN number, and/or subframe number.In this embodiment, two or more subsets of eREGs may be predefined withindexes and/or the index of each subset may be configured as a functionof at least one of system parameters. For example, four subsets may bedefined with modulo J_(sub) for the eREG #n so that J_(sub) subsets maybe defined. If J_(sub=)4, the subsets may be defined as: index −0:subset0={eREGs satisfying that n mod 4=0}; index −1: subset1={eREGssatisfying that n mod 4=1}; index −2: subset2={eREGs satisfying that nmod 4=2}; and/or index −3: subset3={eREGs satisfying that n mod 4=3}.When the subset of eREGs for blocking may be defined as a function ofone or more system parameters, the subset index may be implicitlyindicated by at least one of the system parameters. For example, thesubset index may be defined by modulo operation of cell-ID (e.g.,index-i where i may be defined as Cell-ID mod 4).

The starting symbol of the ePDCCH may be configured as follows (e.g.,according to or based on the ePDCCH search spaces). For example, in anembodiment, the starting symbol of the WTRU or UE-specific search spacemay be configured or defined according to the associated common searchspace. The associated common search space may imply the common searchspace monitored in a subframe together with the WTRU or UE-specificsearch space from a WTRU or UE. Additionally, there may be differenttypes (e.g., two types) of associated common search spaces including,for example, a PDCCH common search space and an ePDCCH common searchspace.

According to an example embodiment, if a PDCCH common search space maybe monitored in a subframe with ePDCCH WTRU or UE-specific search space,one or more of the following may apply and/or may be used or provided.The ePDCCH WTRU or UE-specific search space starting symbol may beconfigured according to the transmission mode configured for a WTRU orUE. For example, if a WTRU or UE may be configured with a legacytransmission mode (e.g., TM 1˜9), the WTRU or UE may follow or use theCIF in PCFICH to figure out or determine the starting symbol for ePDCCHregardless of the DCI format. If the configured transmission mode may bea different transmission mode (e.g., TM-10 (a CoMP transmission mode)),a WTRU or UE may be informed and/or may receive via higher layer theePDCCH starting symbol regardless of the DCI format. In an embodiment,the ePDCCH starting symbol may be dependent on the DCI format such thatif DCI format 2D may be used, the WTRU or UE may follow or use thehigher layer configured ePDCCH starting symbol, otherwise the WTRU or UEmay follow or use the CIF in PCFICH.

Additionally, according to an example embodiment, if an ePDCCH commonsearch space may be monitored in a subframe with an ePDCCH WTRU orUE-specific search space, one or more of following may apply and/or maybe provided and/or used. For example, the ePDCCH WTRU or UE-specificsearch space starting symbol may be the same as the starting symbol forthe ePDCCH common search space. Furthermore, the ePDCCH WTRU orUE-specific search space starting symbol may be configured as a functionof CFI value in PCFICH and ePDCCH common search space starting symbol.The ePDCCH WTRU or UE-specific search space starting symbol may beindependently configured via higher layer signalling irrespective of theePDCCH common search space starting symbol. Additionally, in anembodiment, the ePDCCH WTRU or UE-specific search space starting symbolmay be configured according to the transmission mode configured for aWTRU or UE. For example, based on the transmission mode and/or DCIformat, a WTRU or UE may assume the same starting symbol of ePDCCHcommon search space or may follow or use the starting symbol valueconfigured by higher layer signalling. In particular, according to anembodiment, if a WTRU or UE may be configured with a legacy transmissionmode (e.g., TM1˜9), the starting symbol for the WTRU or UE-specificsearch space may be the same as the starting symbol of the ePDCCH commonsearch space in the subframe and if a WTRU or UE may be configured withanother transmission mode (e.g., TM10 (a CoMP transmission mode)), theWTRU or UE may follow or use the starting symbol value configured viahigher layer signalling.

The starting symbol of the ePDCCH common search space may further beconfigured or defined based on at least one of the following. Accordingto an example embodiment, a WTRU or UE may implicitly detect thestarting symbol of the ePDCCH common search space by decoding the PCFICHin each subframe. Additionally, a fixed starting symbol may bepredefined by assuming that N_(pdcch) OFDM symbols may be occupied forthe legacy PDCCH. As such, the starting symbol for ePDCCH common searchspace may be N_(pdcch)+1. The number of OFDM symbols for PDCCH may alsoinclude N_(pdcch)=0. In a specific carrier type (e.g., a new carriertype in which CRS may not be transmitted in one or more subframes, forexample, may not be transmitted in a subframe except for a subframeincluding PSS/SSS), a WTRU or UE may assume that the number of OFDMsymbols for PDCCH may be N_(pdcch)=0. In such an embodiment, the commonsearch space starting symbol may be broadcasted in PBCH or SIB-x suchthat the starting symbol indicated in a broadcasting channel may be usedfor ePDCCH candidate demodulation in the ePDCCH common search space.

An enhanced control channel element (eCCE) may be described herein.Assuming for a given subframe i, an eCCE comprising a number of eREGsmay be: N_(eREGs)(i), and, for each eREG j, the number of available REsis K_(REs)(i, j), the total number of available REs for one eCCE may be:

${N_{eCCEs}(i)} = {\sum\limits_{j = 1}^{N_{eREGs}{(i)}}\;{{K_{REs}( {i,j} )}.}}$

A first category may be considered where the number of available REs forj^(th) eREG (e.g., K_(REs)(i)j)) may vary due to some REs for otherpurposes such as reference signals, PDCCH, PSS/SSS, and the like and mayresult in changing the effective coding rate. One or more embodimentsdescribed herein may be used, for example, to keep a similar effectivecoding rate for a given DCI payload.

For example, the number of N_(eREGs) may be fixed (e.g., N_(eREGs)=4)per eCCE, so that the starting point of eCCEs may be easily determined(e.g., the starting points of eCCEs may be the same). Since a fixednumber of N_(eREGs) per eCCE may be used, the available REs may bechanged. To increase the coverage with the fixed N_(eREGs) number pereCCE, one or more of the following may be used and/or applied. Forexample, transmission power per eCCE may be defined as a function of theavailable number of REs, where the reference number of REs per eCCE maybe N_(eCCE). For example, if N_(eCCE)=36 and the available number of REsmay be K_(REs)=18 for a specific eCCE, the additional transmission poweradded from the original transmission power may be defined as

${P_{eCCE}\lbrack{dB}\rbrack} = {10\;\log_{10}{\frac{N_{eCCE}}{K_{REs}}.}}$From predefined power boosting rules, a WTRU or UE may assume the powerratio between the reference signal and ePDCCH REs for its demodulationprocess. The fixed number of N_(eREGS) may be separately definedaccording to the ePDCCH transmission type and/or search space type. Forexample, N_(eREGs)=3 may be used for localized transmission andN_(eREGs)=4 may be used for distributed transmission. A smallerN_(eREGs) may be used for localized transmission since beamforming gainand/or frequency selective scheduling may be achieved for localizedtransmission. A distributed transmission may rely on frequency diversitygain with channel coding. A different value of N_(eREGs) may be used fora common search space and WTRU or UE-specific search space. For example,N_(eREGs)=6 may be used for a common search space and N_(eREGs)=4 may beused for a WTRU or UE-specific search space. The eCCE aggregation levelswithin ePDCCH search space may vary according to subframe, where theaggregation levels may be implicitly derived from the reference signalconfiguration for a specific subframe. The aggregation levels may bedefined as a function of a positive integer number N_(AL). For example,a search space for a WTRU or UE may be defined as N_(AL)·{1, 2, 4, 8}.If N_(AL)=2 in a specific subframe, a WTRU or UE may need to monitorePDCCH with the aggregation levels 2, e.g., {1, 2, 4, 8}={2, 4, 8, 16 }.N_(AL) may be configured by a higher layer according to a subframe ordefined implicitly according to the configuration of the subframeincluding reference signal, broadcast channels, and/or synchronizationsignals. N_(AL) may be signaled in the legacy PDCCH (e.g., if it may beconfigured) or unused DCI bits carried on ePDCCH.

A variable number of N_(eREGs) per eCCE may be used, for example, tokeep a similar effective coding rate. Since the ePDCCH decodingcandidate may be based on the eCCE level, the available number of REsfor an eCCE may be changed if a different number of N_(eREGs) may bemapped. If a larger number of N_(eREGs) may be mapped per eCCE, theeffective coding rate may be lower so that channel coding gain may beincreased as a result. That is, a larger number of N_(eREGs) may bemapped if the available number of REs gets smaller per eCCE in aspecific subframe due to the puncturing of ePDCCH REs. The variablenumber of N_(eREGs) may be defined as described herein. For example,N_(eREGs) may be configured by an eNB and may be informed to a WTRU orUE via a broadcasting channel(s) and/or higher layer signal(s).N_(eREGs) may be configured independently per subframe with a dutycycle. For example, 10 ms and 40 ms duty cycles may be used. Two or morenumber of N_(eREGs) may be defined and one of them may be selectedaccording to the CSI-RS and ZP-CSI-RS configuration. In an example,N_(eREGs) ⁰ and N_(eREGs) ¹ may be predefined and one of them may beselected in the following manner: N_(eREGs) ⁰ may be used if no CSI-RSand ZP-CSI-RS may be configured; and N_(eREGs) ¹ may be used if CSI-RSand/or ZP-CSI-RS may be configured.

Since the number of REs for eREGs may be variable, the number of REs foreCCE could be also variable. An eCCE may be defined differentlyaccording to ePDCCH transmission mode (i.e., distributed transmissionand localized transmission). For example, N_(eREGs)=4 may be used forlocalized transmission and N_(eREGs)=2 may be used for distributedtransmission. In an embodiment, the N_(eREGs) may be configurable by eNBvia broadcasting (MIB or SIB-x) and/or higher layer signalling.

In another embodiment, the N_(eREGs) may be different according to thesubframe as described herein. The N_(eREGs) value may be changed if asubframe includes CSI-RS and/or zero-power CSI-RS. For example,N_(eREGs)=4 may be used in the subframe not including CSI-RS and/orzero-power CSI-RS and N_(eREGs)=6 may be used in the subframe includingCSI-RS and/or zero-power CSI-RS. The N_(eREGs) value may be differentaccording to the reference signal overhead including zero-power CSI-RSsuch that the N_(eREGs) value may become larger if reference signaloverhead goes higher. For example, N_(eREGs)=4, if reference signaloverhead may be less than 15% within PDSCH region in a subframe;N_(eREGs)=5, if reference signal overhead may be between 15% and 20%within PDSCH region in a subframe; N_(eREGs)=6, if reference signaloverhead may be between 20% and 30% within PDSCH region in a subframe;N_(eREGs)=5, if reference signal overhead may be larger than 30% withinPDSCH region in a subframe, the reference signal overhead may be definedas “number of PDSCH REs/number of reference signals,” and the like. Inan embodiment, the eREG and eCCE may be the same in a specific ePDCCHtransmission mode such as localized transmission of ePDCCH.

Another category may be considered where the number of N_(eREGs) (i) maybe fixed per eCCE, for example, so that the starting point of eCCEs maybe the same. To maintain an effective coding rate for a DCI payload, thenumber of available REs for a jth eREG (e.g., K_(REs) (i,j)) may befixed for each eREG by transmitting ePDCCH on those REs for otherpurposes such as reference signals, PDCCH, and/or PSS/SSS, and applyingspecial pre-coding or mutual orthogonal patterns to both ePDCCH andnon-ePDCCH. At the receiver side after de-precoding by the WTRU or UE,ePDCCH may be separated and the similar effective coding rate for agiven DCI payload may be maintained.

When assuming the number of N_(eREGs)(i) may vary per eCCE, to maintainthe similar effective coding rate for a given DCI payload, instead ofmaking the number of available REs for j^(th) eREG (e.g., K_(REs) (i,j)) to be fixed for part of eREGs, e.g., as described above, at thereceiver side (e.g., after de-precoding by the WTRU or UE) ePDCCH may beseparated and the similar effective coding rate for a DCI payload may bemaintained. The number of eREGs used to for transmitting ePDCCH andnon-ePDCCH may adapt so that

${N_{eCCEs}(i)} = {\sum\limits_{j = 1}^{N_{eREGs}{(i)}}\;{K_{REs}( {i,j} )}}$may be kept for each CCE.

Additionally, eCCE definition may be different according to ePDCCHsearch spaces. In such an embodiment, the eCCE may be definedrespectively for the WTRU or UE-specific search space and the commonsearch space in following manner. For example, an eCCE definition for aWTRU or UE-specific search space may satisfy one or more of followingproperties. 16 eREGs may be defined per PRB-pair irrespective of theCP-length and subframe type. 4 or 8 eREGs may be grouped to form an eCCEaccording to the CP-length and subframe type. 4 eREGs may be grouped toform an eCCE for a normal CP with a normal subframe and/or a normal CPwith special subframe configurations {3, 4, 8}. In an embodiment, 8eREGs may be grouped to form an eCCE in for a normal CP with specialsubframe configurations {2, 6, 7, 9}, an extended CP with normalsubframe, and/or an extended CP with special subframe configurations {1,2, 3, 5, 6}. Furthermore, 4 or 8 eREGs may be grouped to form an eCCEaccording to the CP-length, subframe type and/or common search spacetype. For example, in such an embodiment, if a WTRU or UE may monitor aPDCCH common search space in a subframe, the number of eREGs per eCCEfor a WTRU or UE-specific search space may be 8 while the number ofeREGs per eCCE for a WTRU or UE specific search space may be 4 if anePDCCH common search space may be monitored together with ePDCCH WTRU orUE-specific search space.

Additionally, an eCCE definition for common search space may satisfy oneor more of following properties. In an embodiment, 16 eREGs may bedefined per PRB-pair irrespective of the CP-length and subframe type. 4or 8 eREGs may also be grouped as the same the WTRU or UE-specificsearch space. Furthermore, 4 or 8 eREGs may be grouped to form an eCCEaccording to the number of available REs (e.g., n_(ePDCCH)). In such anembodiment, the number of available REs may be counted in each subframewithin a PRB-pair that may not include PSS/SSS and/or PBCH.Additionally, if n_(ePDCCH) may be smaller than a threshold predefined(e.g., 104), 8 eREGs may be grouped to form an eCCE, otherwise 4 eREGsmay be used and/or grouped together.

Resource mapping may be provided, which may include eREG-to-eCCEmapping. For example, an eCCE may be formed with one or more eREGs andthe group of eREGs may be differently formed according to the ePDCCHtransmission modes (e.g., ePDCCH Mode-1 and ePDCCH Mode-2).

FIG. 20 illustrates an example embodiment of eCCE-to-eREG mapping inePDCCH according to localized and distributed allocation (e.g., ifport-7 and port-8 may be used). For example, the eREG may be defined asshown in FIG. 20 where N=1 and M=14-N_(PDCCH) may be used. The eREGnumber may also be defined as at least one of following: increasingorder from lowest frequency within ePDCCH PRBs (0˜N_(tot)(k)−1), whereN_(tot)(k) may denote the number of eREGs in a subframe k andN_(tot)=N_(eRB)×M_(REG) and the M_(REG) may denote the number eREGs in aPRB-pair and M_(REG)=12 as shown in FIG. 20; decreasing order fromlowest frequency within ePDCCH PRBs (0˜N_(tot)(k)−1); random numbergeneration within (0˜N_(tot)(k)−1) and virtual eREG and physical eREGmapping may be defined; eREG number may be (f, r) where f and r maydenote subcarrier index within a PRB-pair and ePDCCH PRB numberrespectively, the eREG #13 may be expressed as eREG (1, 1), the rangeoff may be 0˜11, or may be 0˜N_(eRB)−1, and eREG #=r·12+f.

For eCCE-to-eREG mapping in shared PRB, at least one of the followingmethods (e.g., contiguous allocation (Mapping-1), interleaved allocation(Mapping-2), hybrid allocation (Mapping-3), and/or the like) may beused. In contiguous allocation (Mapping-1), N_(eREGs) contiguous eREGsmay be aggregated for eCCE definition, therefore the eCCE numbers may beallocated as eCCE #n=eREGs #{n·N_(eREGs), . . . , (n+1)·N_(eREGs)−1}.For example, if N_(eREGs)=4 and n=0, the eCCE #0=eREGs #{0,1,2,3}. Insuch an embodiment, the total number of eCCEs (M_(eCCE)) may be definedas

$M_{eCCE} = {\lfloor \frac{N_{tot}}{N_{eREGs}} \rfloor.}$FIG. 21 shows such an example (e.g., FIG. 21 illustrates an exampleembodiment of eCCE-to-eREG mapping with contiguous allocation).

In an interleaved allocation (e.g., Mapping-2), N_(eREGs) interleavedeREGs may be aggregated for eCCE definition, therefore the eCCE numbersmay be allocated as eCCE#n=eREGs #{π(n·N_(eREGs)) , . . . ,π((n+1)·N_(eREGs−)1)} where π(·) denotes interleaved sequence from 0 toM_(eCCE)−1 . The interleaved sequence π(·) may be generated byN_(eREGs)×M_(eCCE) block interleaver. If N_(eREGs)=4 and M_(eCCE)=9, 4×9block interleaver may be defined as shown in the FIG. 22 (e.g., FIG. 22illustrates an example of a block interleaver). In the blockinterleaver, the interleaved sequence may be generated by writing asequence in row first and read in column first. As such, the interleavedsequence from block interleaver illustrated in FIG. 22 may beπ=0,9,18,27,1,10,19,28, . . . , 8,17,26,35, which may be expressed as

${{\pi(n)} = {{( {n \cdot M_{eCCE}} ){mod}\; N_{tot}} + \lfloor \frac{n \cdot M_{ECCE}}{N_{tot}} \rfloor}},{n = 0},\ldots\mspace{14mu},{N_{tot} - 1.}$The interleaved sequence π(·) may be generated by length-N_(tot) randomsequence where the random sequence may be predefined and both WTRU or UEand eNB may know the sequence. A column permutation may be used, e.g.,in order to further randomize the permutation sequence.

In hybrid allocation (Mapping-3), a subset of contiguous sequences maybe reserved for localized transmission and the other eREGs may be usedfor distributed allocation. For example, a subset of columns in a blockinterleaver may be reserved for localized transmission, as shown in FIG.23 (e.g., FIG. 23 illustrates hybrid allocation by using blockinterleaver), where eCCE #{4, 5, 6, 7} may be used for localizedtransmission and the other eCCEs may be distributed allocation. Togenerate localized eCCEs, N_(eREGs) contiguous eCCEs may be used. Fromthis operation, N_(eREGs) contiguous distributed allocation based eCCEsmay become localized N_(eREGs) eCCEs. To generate both localized anddistributed eCCEs, an eNB may define M_(eCCE) distributed eCCEs, andreserve N_(eREGs) contiguous or closed eCCEs for localized eCCEs. Acolumn permutation may be used for distributed allocation part tofurther randomize the permutation sequence. From the hybrid allocationshown in FIG. 23, the eCCEs may be defined as shown in FIG. 24. FIG. 24illustrates an example embodiment of a co-existence of localized anddistributed eCCEs.

For eCCE-to-eREG mapping in separate PRB, eREGs may be independentlydefined for localized and distributed transmissions. For example, LeREGs(localized eREGs) may be defined from 0˜N−1, DeREGs (distributed eREGs)may be defined from 0˜K−1, and for LeREGs, contiguous allocation (e.g.,Mapping-1) may be used and/or interleaved allocation (e.g., Mapping-2)may be used for DeREGs. For eCCE-to-eREG mapping in separate PRB, eREGmay be defined for the limited case of distributed transmission and eCCEmay become a minimum resource unit for localized transmission.

The eCCE-to-eREG configuration may be at least one of following: theeCCE allocation (e.g., Mapping-1, Mapping-2, or Mapping-3) may bepredefined, the mapping method may be different according to thesubframe index and/or SFN, the mapping method may be configurable byhigher layer signalling, the mapping method may be different accordingto the ePDCCH PRB-pairs, and/or the like. According to an exampleembodiment, if N_(eRB) may be available for ePDCCH transmission, asubset of N_(eRB) may use the Mapping-1 and other ePDCCH PRB-pairs(e.g., the rest of ePDCCH PRB-pairs) may use the Mapping-2. In thisembodiment, N_(eRB) may be be separately defined for each mappingmethod.

If 16 eREGs may be available per PRB-pair and one eCCE may be defined bygrouping of four eREGs, 4 eCCEs may be defined per PRB-pair for ePDCCHlocalized transmission since the eCCE may be defined within a PRB-pairfor localized transmission. In an embodiment, among 16 eREGs,consecutive 4 eREGs may be grouped to form a localized eCCE. TheeCCE-to-eREG mapping rule may be the same in each PRB-pair configured asePDCCH resource. The consecutive 4 eREGs within a PRB pair with the samestarting points irrespective of the cell may be used. For example, theeREG-to-eCCE mapping rule may be the following for each cell:eCCE(n)={eREG(k), eREG(k+1), eREG(k+2), eREG(k+3)};eCCE(n+1)={eREG(k+4), eREG(k+5), eREG(k+6), eREG(k+7)}; eCCE(n+2)={eREG(k+8), eREG(k+9), eREG(k+10), eREG(k+11)}; and/oreCCE(n+3)={eREG(k+12), eREG(k+13), eREG(k+14), eREG(k+15)}. Theconsecutive 4 eREGs within a PRB pair with different starting points maybe used. The starting point of the eREG may be defined as aconfiguration via higher layer signaling or a function of at least oneof the system parameters such as physical cell ID and subframe/SFNnumber. In the following example, the offset may be configured viahigher layer signaling or defined as a function of at least one of thesystem parameters. In an example, eCCE(n)={eREG((k+i+offset)mod16),i=0,1,2,3 }; eCCE(n+1)={eREG((k+4+i+offset)mod16), i=0,1,2,3 };eCCE(n+2)={eREG((k+8+i+offset)mod16), i=0,1,2,3}; and/oreCCE(n+3)={eREG((k+12+i+offset)mod16), i=0,1,2,3}.

Additionally, in an embodiment, among 16 eREGs, mutually exclusive 4eREGs may be grouped to form an eCCE so that 4 eCCEs may be defined perPRB-pair and each eCCE may include mutually exclusive 4 eREGs. Themutually exclusive 4 eREGs may be selected by using one or moreembodiments described herein to form an eCCE. For example, aninterleaved mapping may be used for eREG-to-eCCE mapping. eREG-to-eCCEmapping may be based on block interleaver (e.g., interlaced mapping).The followings may be examples of the eREG-to-eCCE mapping:eCCE(n)={eREG(k), eREG(k+4), eREG(k+8), eREG(k+12)};eCCE(n+1)={eREG(k+1), eREG(k+5), eREG(k+9), eREG(k+13)};eCCE(n+2)={eREG(k+2), eREG(k+6), eREG(k+10), eREG(k+14)}; and/oreCCE(n+3)={eREG(k+3), eREG(k+7), eREG(k+11), eREG(k+15)}. An interleavedmapping may be used for eREG-to-eCCE mapping based on randominterleaver. The interleaved sequence may be predefined or configuredvia higher layer signaling. If the interleaved sequence per eCCE in aPRB-pair may be defined as π₁={0,4,8,12}, π₂={1,5,9,13},π₃={12,6,10,14}, and π₄={3,7,11,15}, where π_(j), j=0,1,2,3 may be usedto form eCCE (n+j), eCCE(n+j)={eREG(k+π_(j)(1)), eREG(k+π_(j)(2)),eREG(k+R_(j)(3)), eREG(k+π_(j)(4))}. The interleaved sequence may bedefined as a function of at least one of system parameters, including aphysical cell ID, a subframe, and/or an SFN number.

Antenna port mapping may also be provided and/or used. For example, theantenna ports {7, 8, 9, 10} or a subset of them may be used for ePDCCHtransmission and the antenna ports {107, 108, 109, 110} may be usedinterchangeably with the antenna ports {7, 8, 9, 10} as the time and/orfrequency location with orthogonal cover code may be the same. In anembodiment, since the antenna ports 7˜10 may be used for eREG and/oreCCE demodulation, the antenna port mapping may be defined according tothe eREG/eCCE locations. FIG. 25 illustrates an example embodiment ofantenna port mapping for eREG/eCCE. As shown in FIG. 25, the eREG/eCCEmay be mapped onto antenna ports. FIG. 25 also shows that the number ofantenna ports available may be different according to the configuration.

The available number of antenna ports (N_(port)) may be defined asdescribed herein. The N_(port) may be semi-statically configured for thesubframes and the ePDCCH PRB-pairs. Therefore, a WTRU or UE may assumethat ePDCCH may not be transmitted in the RE position for the antennaports within N_(port). For example, if N_(port)=4, 24 RE positions in aPRB-pair in FIG. 25 may be reserved and ePDCCH may not be transmitted inthose RE positions. If N_(port)=2 then 12 RE positions may be reservedand ePDCCH may be be transmitted in the RE positions for Port-9 andPort-10. The N_(port) may be predefined as four so that a WTRU or UE mayassume that ePDCCH may not be transmitted in the RE positions for fourantenna ports. The N_(port) may be different according to the ePDCCHPRB-pair number. For example, N_(port)=2 may be used in the ePDCCH PRB#0 and N_(port)=4 may be used in the ePDCCH PRB #1. The N_(port) may beconfigured differently according to the ePDCCH PRB-pair with ePDCCHtransmission mode. If ePDCCH PRB #{0, 1, 2} may be used for localizedtransmission, the N_(port)=4 may be used for those ePDCCH PRBs andN_(port)=2 may be used for the ePDCCH PRBs for distributed transmissionor vice versa. The N_(port) may also be separately configurable for eachePDCCH PRB-pair and/or ePDCCH transmission mode.

Additionally, an antenna port may be allocated for eREG/eCCE based on oraccording to at least one of following. A WTRU or UE may assume that aneREGs/eCCE associated with the WTRU or UE in a “same PRB-pair” may betransmitted on the same antenna port. For example, if eREGs/eCCEs #{n,n+1, n+2, n+3} may be used for a WTRU or UE, the WTRU or UE may assumethat the eREGs may be transmitted in one antenna port (e.g., Port-7).The antenna port may be semi-statically configured via higher layersignalling. In such an embodiment, the antenna port may be the same forthe WTRU or UE across each of the ePDCCH PRB-pairs. The antenna port maybe defined as the lowest eREG/eCCE index in the same PRB-pair. Forexample, if eREGs/eCCEs #{n, n+3, n+6, n+9} may be used for a WTRU orUE, the antenna port for eREG/eCCE #{n} may be used for othereREGs/eCCEs. The antenna port may be defined as a function of C-RNTI.For example, modulo-4 or 2 of the C-RNTI may indicate the allocatedantenna port for the WTRU or UE. The antenna port may be the same forthe WTRU or UE across the ePDCCH PRB-pairs in such an embodiment. If themodulo-4 operation may be used, a WTRU or UE may assume that one of theantenna ports 7˜10 may be used for the WTRU or UE, otherwise one of theantenna ports 7˜8 may be used. The antenna port may be defined as afunction of C-RNTI with a CDM group and the CDM group may be configuredby higher layer. For example, a WTRU or UE may be configured by higherlayer to monitor ePDCCH within a CDM group 2 in which Port-9 and Port-10may be available and the C-RNTI for the WTRU or UE may indicate to usePort-9 after modulo-2 operation. As such, the C-RNTI may indicate whichorthogonal cover code may be used between [+1+1] and [+1−1] within a CDMgroup and an eNB may choose a CDM group. The antenna port may be definedas a function of C-RNTI and PRB-pair index. For example, modulo 4 or 2of (C-RNTI+PRB index) may indicate the allocated antenna port for theWTRU or UE.

A WTRU or UE may assume that eREGs/eCCEs associated with the WTRU or UEin a “precoding resource granularity (PRG)” may be transmitted on thesame antenna port. For example, if a WTRU or UE demodulates multipleeREGs in a PRG the WTRU or UE may assume that the same antenna port maybe used for the eREGs in the PRG. The WTRU or UE may assume that thesame precoder may be used for the antenna port within PRG. The PRG sizemay be different according to the system bandwidth. Table 12 shows anexample embodiment of the PRG size for ePDCCH.

TABLE 12 PRG size for ePDCCH System Bandwidth (N_(RB) ^(DL)) PRG size(P′) ≤10 1 11-26 2 27-63 3  64-110 2

The PRB size may be 1 for system bandwidth candidate and a WTRU or UEmay assume that each of the antenna ports in the PRB size use the sameprecoder, for example, such that the channels across antenna ports maybe interpolated. For example, if antenna ports 7 and 9 within a PRG sizemay be used for ePDCCH demodulation at a WTRU or UE receiver, the WTRUor UE may assume that antenna ports 7 and 9 may be transmitted in thesame virtual antenna port so that the estimated channels from port 7 and9 may be interpolated. The antenna port may be defined as a lowesteREG/eCCE index within a PRG. For example, if eREGs/eCCEs #{n, n+8,n+16, n+24} may be used for a WTRU or UE, the antenna port for eREG/eCCE#{n} may be used for other eREGs/eCCEs. The antenna port may further bedefined as a function of C-RNTI. For example, modulo 4 or 2 of theC-RNTI may indicate the allocated antenna port for the WTRU or UE. In anembodiment, the antenna port may be the same for the WTRU or UE acrossePDCCH PRB-pairs in this case as well. Additionally, the antenna portmay be defined as a function of C-RNTI and PRG index. For example,modulo 4 or 2 of (C-RNTI+PRG index) may indicate the allocated antennaport for the WTRU or UE.

A WTRU or UE may also assume that eREGs/eCCEs associated with the WTRUor UE in a same PRB-pair may be transmitted on different antenna portsand the antenna ports for each eREG/eCCE may be defined based on oraccording to at least one of following methods herein. For example, aneREG/eCCE location may be one-to-one mapped onto an antenna portaccording to the available number of antenna ports. If four antennaports may be available in the PRB-pair, the eREGs #{n, n+1, n+2} may bemapped onto Port-7, eREGs #{n+3, n+4, n+5} may be mapped onto Port-8,eREGs #{n+6, n+7, n+8} may be mapped onto Port-9, and the rest may bemapped on to Port-10. If two ports may be available, eREGs #{n, n+1,n+2, n+5} may be mapped on to Port-7 and the other eREGs may be mappedon to Port-8. The associated antenna port number may be definedaccording to the eREG/eCCE location and aggregation level for a WTRU orUE. For example, eREGs #{n, n+1, n+2 } may be mapped onto Port-7 andeREGs #{n+3, n+4, n+5} may be mapped onto Port-8 if three REGs may bedemodulated together. If eREGs #{n, n+1, n+2, n+3, n+4, n+5} may bedemodulated together, the Port-7 may be used and Port-8 may not be theantenna port for eREGs {n+3, n+4, n+5} (e.g., anymore). An eREG/eCCElocation may be one-to-one mapped onto an antenna port according to theavailable number of antenna ports. The association rule betweeneREG/eCCE and antenna ports may be configured by an eNB. For example, iffour antenna ports may be available in the PRB-pair, the eREGs/eCCE #{n,n+1, n+2} may be mapped onto Port-7, and eREGs/eCCE #{n+3, n+4, n+5} maybe mapped onto Port-8 for a WTRU or UE. For another WTRU or UE, theeREG/eCCE #{n, n+1, n+2} may be mapped onto Port-8, and eREG/eCCE #{n+3,n+4, n+6} may be mapped onto Port-7.

The association rule may be configured according to at least one offollowing embodiments. For example, an eNB may configure the associationrule via WTRU or UE-specific higher layer signaling. The associationrule may be configured as a function of RNTI (e.g., C-RNTI) so that aWTRU or UE may implicitly obtain the association rule. In such a case,there may be a different association rule according to RNTI type, e.g.,even for a single WTRU or UE. In an example, a DCI associated with aC-RNTI may use association rule 1 and another DCI associated with anSPS-RNTI may use association rule 2. A modulo operation may be used todefine an association rule such that the number of an association rule(e.g., n_association) may be used for a modulo operation as a functionof RNTI. The association rule for a DCI associated with a specific RNTImay be defined as association rule number=(RNTI) modulo n_association.The association rule may be configured as a function of RNTI incombination with other parameters, which may include one or more of aCell-ID, subframe number, and/or SFN. The association rule may also befixed for a common search space and configurable for a WTRU orUE-specific search space.

In an embodiment, a WTRU or UE may assume that a single antenna portconfigured via higher layer signaling may be associated with eacheREG/eCCE in localized transmission. A predefined one-to-one mappingbetween eREG/eCCE to antenna port may be used for distributedtransmission.

Resource element (RE) mapping (e.g., puncturing and/or rate-matching)may be provided and/or used as described herein. For example, modulatedsymbols of a DCI after channel coding may be mapped onto ePDCCH REs.Since the ePDCCH REs may be located in an RE location, the mapping rulemay be defined in a coding chain perspective. In a coding chain aspect,RE mapping rules may include puncturing and/or rate-matching, asdisclosed herein. Puncturing and/or rate-matching may be provided asfollows.

Coded bits (c₁, . . . , c_(N)) may be an output of a channel encoderwith a DCI payload as an input, where the channel encoder may be achannel code, such as a turbo code, convolutional code, reed-mullercode, etc. The coded bits may include a CRC attachment, for example, 16bits masked with RNTI. Modulated symbols (x₁, . . . , x_(M)) may be anoutput of a mapper such that the coded bits may be modulated to amodulation scheme such as BPSK, QPSK, 16 QAM, 64 QAM, and the like.According to the modulation scheme, the modulated symbol sequence M maybe equal to or smaller than N. In RE mapping, the modulated symbols x₁,. . . , x_(M) may be mapped to ePDCCH REs, for example, in a frequencyfirst or time first manner where puncturing may imply or may providethat if a RE in ePDCCH may be occupied for another signal, the modulatedsymbol for the RE may not be transmitted. For example, if x_(k), k≤M maybe mapped on a specific ePDCCH RE according to the mapping rule and theePDCCH RE may be occupied for another purpose, x_(k) may not betransmitted and the next mapping may be started from x_(k+1).Rate-matching may imply or may provide that the next mapping to theavailable RE not used for another purpose may be started from x_(k) inthe same situation. As an example, if there may be six modulated symbols{x₁, x₂, x₃, x₄, x₅, x₆} to be transmitted and the ePDCCH REs for x₂ andx₄ may be occupied for other purpose, {x₁, x₃, x₅, x₆} may betransmitted if a puncturing scheme may be used and {x₁, x₂, x₃, x₄} maybe transmitted if rate-matching may be used.

Since the puncturing scheme may lose systematic bits if a convolutionaland/or turbo code may be used, the decoding performance, in anembodiment, may be worse than a rate-matching scheme if coding rate maybe high. Puncturing may provide robustness if the occupied REsinformation may not be synched between eNB and the WTRU or UE. Channeldecoding may fail if occupied RE information may not be synched betweeneNB and WTRU or UE for a rate-matching scheme. The puncturing andrate-matching rules based on a purpose of occupied RE may be providedand/or used.

In an embodiment, the rate-matching scheme may be used for the REsoccupied and configured in cell-specific or group-specific manner andthe puncturing scheme may be used for the REs occupied and configured inWTRU or UE-specific manner. In an example for rate-matching, the REs maybe occupied by PDCCH (or PDCCH region), CRS (cell-specific referencesignal), ePDCCH DM-RS, PRS, PSS/SSS (primary synchronizationsignal/secondary synchronization signal), and/or PBCH. For puncturing,the REs may be occupied by CSI-RS, zero-power CSI-RS. In an example forrate-matching, the REs may be occupied by CRS, PRS, PSS/SSS, and/orPBCH. For puncturing, the REs may be occupied by ePDCCH DM-RS, CSI-RS,and/or zero-power CSI-RS.

The rate-matching and puncturing rules may be defined according to thesearch space. For example, common search space may use puncturing schemeand WTRU or UE-specific search space may use rate-matching scheme sothat the common search space may become more robust to the error ofoccupied RE information, and vice-versa. In an example forrate-matching, each RE may be occupied by other signals in WTRU orUE-specific search space. For puncturing, each RE may be occupied byother signals in common search space. Additionally, in an example forrate-matching, each RE may be occupied by other signals in common searchspace. For puncturing, each RE may be occupied by other signals in WTRUor UE-specific search space.

According to an example embodiment, the rate-matching and puncturingrules may be defined according to the ePDCCH transmission scheme ortechnique such as localized and/or distributed transmission. Forexample, rate-matching may apply for each RE occupied by other signalsin the eCCEs for localized transmission and puncturing may apply foreach RE occupied by other signals in the eCCEs for distributedtransmission, or vice-versa.

The rate-matching and puncturing rules may also be defined according tosemi-static signals and dynamic signals. In an example forrate-matching, the REs may be occupied by fixed cell-specific signalsincluding CRS, PSS/SSS, and/or PBCH. For puncturing, the REs may beoccupied by semi-static or dynamic configuration including PDCCH,CSI-RS, DM-RS, and/or PRS. In an example for rate-matching, the REs maybe occupied by semi-static or dynamic configuration including PDCCH,CSI-RS, DM-RS, and/or PRS. For puncturing, the REs may be occupied byfixed cell-specific signals including CRS, PSS/SSS, and/or PBCH.

In an embodiment, the rate-matching and puncturing rules may also bedefined according to the ePDCCH search spaces. For example, therate-matching and puncturing rules may be defined differently if thesearch space may be a WTRU or UE-specific search space or common searchspace (e.g., different rate-matching and/or puncturing rules may beapplied for a WTRU or UE-specific search space than for a common searchspace). For the WTRU or UE-specific search space, the REs may beconfigured as ePDCCH WTRU or UE-specific search space resources wherethe REs that may collide with PDCCH, CSI-RS, zero-power CSI-RS, andDM-RS may be rate-matched around.

For the common search space, one or more of the followings may apply.For example (e.g., for the REs configured as ePDCCH common search spaceresources), the REs located in the CRS position may be rate-matchedaround. In such an embodiment, the number of CRS port may be fixed asfour irrespective of the number of CRS port detected in PBCH. As such, aWTRU or UE may assume that the REs located in the CRS ports 0-3 may berate-matched around when demodulating ePDCCH common search space.Additionally, in such an embodiment, a WTRU or UE may follow and/or usethe number of CRS ports detected in PBCH for rate-matching of the REslocated in the CRS ports.

Additionally, for the common search space where the REs may beconfigured as ePDCCH common search space resources, the REs located inthe CSI-RS and zero-power CSI-RS may be punctured. As such, if a WTRU orUE may be configured with CSI-RS and/or zero-power CSI-RS, the REs inthose locations may be punctured.

In an example embodiment, for the common search space and the PDCCH, ifa WTRU or UE may monitor a PDCCH common search space together with anePDCCH common search space, the WTRU or UE may rate-match around for theREs located in the PDCCH locations. Otherwise, the WTRU or UE mayrate-match around for the REs located in the OFDM symbols below theePDCCH common search space starting symbols.

According to an embodiment, a search space design may be provided and/orused as described herein. For example, a search space for a single DLcarrier may be disclosed. A WTRU or UE may monitor ePDCCHs via blinddecoding such that multiple blind decoding attempts may be used persubframe. The candidates for blind decoding attempts from a WTRU or UEpoint of view may be hereafter called a search space. At least one oftwo types of search space may be defined for ePDCCH, such as WTRU orUE-specific search space (USS) and common search space (CSS). The commonsearch space in ePDCCH may carry DCIs related to a group of UEs and/orthe UEs in a cell such as broadcasting/multi-casting, paging, grouppower control, etc. The WTRU or UE-specific search space may carry DCIsfor unicast traffic for uplink and/or downlink.

From a WTRU or UE perspective, there may be at least two search spacesand the location for search spaces may be defined using at least one offollowing configurations. In a configuration (e.g., configuration 1),both USS and CSS may be provided or used in legacy PDCCH and a WTRU orUE may monitor USS and CSS. In such a configuration, a WTRU or UE maymonitor USS and/or CSS in the legacy PDCCH region. This configurationmay be the same as, or similar to, the Release 8 PDCCH configuration. Inan additional configuration (e.g., configuration 2), both USS and CSSmay be provided or used in ePDCCH and a WTRU or UE may monitor USS andCSS (e.g., a WTRU or UE may monitor USS and/or CSS in the ePDCCHregion). In yet another configuration (e.g., configuration 3), USS inlegacy PDCCH may be provided or used and CSS in ePDCCH may be providedor used (e.g., a WTRU or UE may monitor CSS in legacy PDCCH regionand/or USS in ePDCCH region). Additionally, in a configuration (e.g.,configuration 4), USS in ePDCCH may be provided or used and CSS inlegacy PDCCH may be provided or used where, for example, a WTRU or UEmay monitor CSS in a legacy PDCCH region and USS in an ePDCCH region.Additionally (e.g., in configuration 4), the CSS may be shared withlegacy UEs. In this case, the CCEs from 0 to 15 may be used as CSS in alegacy PDCCH region. In configuration 4, the CSS may be defineddifferently. For example, the CCEs from 16 to 31 in legacy PDCCH may beused as CSS for the WTRU or UE configured with ePDCCH for USS. Inanother example configuration (e.g., configuration 5), USS in ePDCCH maybe provided or used and CSS may be split into legacy PDCCH and ePDCCH.According to an additional configuration (e.g., configuration 6), USSmay be split into legacy PDCCH and ePDCCH and CSS in ePDCCH may beprovided or used. Also, in a configuration (e.g., configuration 7), bothUSS and CSS may be split into legacy PDCCH and ePDCCH. In configuration8, USS may be split into legacy PDCCH and ePDCCH, and CSS in legacyPDCCH may be provided or used.

The search space configuration may be defined based on or according toat least one of following. A single configuration may be predefined andthe details of configuration information may be broadcasted in MIBand/or SIB-X. A configuration may be predefined such that a WTRU or UEmay receive the configuration in broadcasting information at least oneof MIB or SIBs. A configuration may be RRC-configured such that a WTRUor UE may be requested to change the search space according to the RRCsignalling. A configuration may also be changed according to the SFNand/or subframe number such that a WTRU or UE may implicitly know theconfiguration in each subframe (e.g., the per subframe configurationinformation may be informed by broadcasting or RRC signalling and/or theper subframe configuration information may be predefined (e.g., subframe#0 and #5)).

An eCCE aggregation level may be defined as the same as legacy PDCCHsuch that the aggregation levels {1, 2, 4, 8} may defined and the numberof blind decoding attempts in total may be 44 without uplinkmulti-antenna transmission (e.g., DCI format 4). The number of REs foran eCCE may be variable unlike CCE in legacy PDCCH, the coding rate forePDCCH according to the aggregation level may vary, thus resulting inePDCCH coverage variation.

Additional aggregation levels may be added to the previous aggregationlevels {1, 2, 4, 8} for ePDCCH for finer ePDCCH link adaptation as shownin the Table 13. For WTRU or UE-specific search space, the aggregationlevels {3, 5, 6, 7} may be added, and {6} may be added for common searchspace for example.

TABLE 13 ePDCCH candidates monitored by a WTRU or UE. Number of ePDCCHSearch space S_(k) ^((L)) candidates Type Aggregation level L Size [ineCCEs] M^((L)) WTRU or 1 6 6 UE-specific 2 12 6 3 18 6 4 8 2 5 11 2 6 122 7 14 2 8 16 2 4 16 4 Common 6 16 4 8 16 2 *Either WTRU or UE-specificsearch space or Common search space may be defined for ePDCCH

Although the number of aggregation levels may be increased, the numberof blind decoding attempts may be kept as before in order not toincrease WTRU or UE receiver complexity. To keep the number of blinddecoding attempts, a subset of aggregation levels may be monitored in asubframe.

TABLE 14 multiple subsets of ePDCCH candidates monitored by a WTRU orUE. Number of ePDCCH candidates Search space S_(k) ^((L)) M ^((L)) TypeAggregation level L Size [in eCCEs] Subset 1 Subset 2 Subset 3 Subset 4WTRU or 1 6 6 6 UE-specific 2 12 6 6 6 3 18 6 4 2 2 2 2 5 180 6 12 14 816 2 2 2 2 16 32 2 2 Common 4 16 4 4 6 16 4 8 16 2 2 2 2 16 32 2 2

Additionally, a WTRU or UE may monitor a subset of aggregation levelsaccording to the subset of ePDCCH candidates shown in the Table 14. Thesubset for ePDCCH monitoring may be configured based on or according toat least one of followings: the subset of ePDCCH aggregation level maybe configured by broadcasting and/or higher layer signalling; referencesignal overhead within ePDCCH resource may implicitly configure thesubset; the subset may be configured differently according to the ePDCCHtransmission mode (e.g., Mode-1 and Mode-2); the subset may beconfigured differently according to the ePDCCH PRB number; and/or thelike.

The number of ePDCCH candidates per aggregation level may be differentaccording to DCI format, ePDCCH resource set, and/or subframe. Forexample, if aggregation level 1 may be more frequently used for DCIformat 0/1A, the larger number of ePDCCH candidates for aggregationlevel 1 may be used as compared with that for aggregation level 2. Thelarger number of ePDCCH candidates may be used for DCI format 2C ascompared with that for aggregation level 1.

Table 14-1 shows an example of DCI format dependent ePDCCH candidate setin which the number of ePDCCH candidates according to the aggregationlevel may be different if different DCI format may be used.

TABLE 14-1 DCI format dependent ePDCCH candidate set Number of ePDCCHSearch space S_(k) ^((L)) candidates M^((L)) Aggregation DCI DCI Typelevel L Size [in eCCEs] format 0/1A format 2C WTRU or 1 6 8 4UE-specific 2 12 4 8 4 8 2 2 8 16 2 2 Common 4 16 4 4 8 16 2 2

A WTRU or UE may attempt to decode 8 ePDCCH candidates with aggregationlevel-1 when the WTRU or UE may monitor DCI format 0/1A. If the WTRU orUE may monitor DCI format 2C, the WTRU or UE may attempt to decode 4ePDCCH candidates.

The number of ePDCCH candidates in each aggregation level may bedifferent according to the DCI format in the WTRU or UE-specific searchspace. Additionally, in an embodiment, the common search space may havethe same number of ePDCCH candidates in each aggregation level,irrespective of the DCI format, for example.

The number of ePDCCH candidates according to the aggregation levels {11,2, 4, 8} may be configured via broadcasting and/or higher layersignalling. In a cell, the ePDCCH candidates may be configured as {6, 6,2, 2} (e.g., the same with legacy PDCCH), while another cell mayconfigure {2, 10, 2, 2} as the ePDCCH candidates, for example. TheePDCCH candidates for aggregation levels may be configured independentlyaccording to the DCI format, or a group of DCI formats. To reduce thesignalling overhead, multiple sets of ePDCCH candidates for aggregationlevels may be defined with indication bits, as illustrated in Table 14-2for example.

TABLE 14-2 ePDCCH candidates for aggregation levels. Number of ePDCCHcandidates Search space S_(k) ^((L)) M^((L)) Aggregation Set 3 Typelevel L Set 0 (00) Set 1 (01) Set 2 (10) (11) WTRU or 1 8 4 8 16 UE-specific 2 4 8 8 0 4 2 2 0 0 8 2 2 0 0 Common 4 — — — — 8 — — — —

In embodiments, among the sets for ePDCCH candidates, one or more set(s)may have the same number of ePDCCH candidates as legacy PDCCH, such as{6, 6, 2, 2} for WTRU or UE-specific search space and/or {4, 2} forcommon search space, for example. One or more of the sets may have noePDCCH candidates for common search space. In this case, a WTRU or UEmay monitor PDCCH candidates as a common search space. One or more ofthe sets may include a subset of aggregation level that may not have thecandidate. For example, {8, 8, 0, 0} may be used so that aggregationlevel 4 and 8 may not be supported in the search space in this case. Thetotal number of blind decoding attempts may be kept the same.

ePDCCH candidate definitions may also be provided and/or used asdescribed herein. A WTRU or UE may be configured to monitor ePDCCH incommon and/or WTRU or UE-specific search space. In an embodiment, theePDCCH candidates the WTRU or UE may monitor in a subframe may bedefined according to the ePDCCH transmission type.

The ePDCCH candidates for WTRU or UE-specific search space may bedefined as follows for ePDCCH localized and/or distributedtransmissions, where N_(eCCE,p,k) may denote the total eCCE number thatmay be available for ePDCCH resource set p. The WTRU or UE-specificsearch space S_(p,k) ^((L)) for ePDCCH resource set p may be defined asL·{(Y_(p,k)+m′) mod └N_(eCCE,p,k)/L┘}+i where i=0, . . . , L−1,m′=m+M_(p) ^((L))·n_(CI), and m=0, . . . ,M_(p) ^((L))−1 . The M_(p)^((L)) may denote the number of ePDCCH candidates for the aggregationlevel L in ePDCCH resource set p. Y_(p,k), which may be a hashingfunction for ePDCCH resource set p, may be defined byY_(p,k)=(A·Y_(k−1))mod D where Y_(p,−1)=n_(RNTI)≠0 , A=39827, D=65537and k=└n_(s)/2┘.

Additionally, the ePDCCH candidates for localized ePDCCH resource setsmay be defined with an offset value (K_(offset)) to distribute ePDCCHcandidates over multiple PRB pairs as much as possible. The same ePDCCHWTRU or UE-specific search space equation may be used for both localizedand distributed ePDCCH. In this embodiment, as an example, the WTRU orUE specific search space S_(p,k) ^((L)) for the ePDCCH resource set pconfigured with localized ePDCCH may be defined asL·{(Y_(p,k)+m′+K_(offset,p)) mod └N_(eCCE,p,k)/L┘}+i. The K_(offset,p)for ePDCCH resource set p, may be configured via higher layer signallingin a WTRU or UE-specific manner. The K_(offset,p) may be defined as afunction of at least one of the following parameters: the aggregationlevel (L); ePDCCH candidate index (m′); the number of total availableeCCE N_(eCCE,k); and/or the number of ePDCCH resource sets K_(set).

In another example, the offset according to the ePDCCH candidate numberand aggregation level may be expressed as L·{(Y_(p,k)+K_(offset,p)(m′))mod └N_(eCCE,p,k)/L┘}+i where the offset (K_(offset,p)) may be definedas a function of the ePDCCH candidate number (m′). Example embodimentsof the definitions of K_(offset,p) may be as follows. In such exampleembodiments (e.g., example equations), m′ and m may be usedinterchangeably.

According to an example embodiment,

${K_{{offset},p}( m^{\prime} )} = \lfloor \frac{m^{\prime} \cdot N_{{eCCE},p,k}}{L \cdot M_{p}^{(L)}} \rfloor$may be used if multiple ePDCCH resource sets may be used. In such anembodiment, the offsets for ePDCCH resource set p may be defined as

${K_{{offset},p}( m^{\prime} )} = \lfloor \frac{m^{\prime} \cdot N_{{eCCE},k,p}}{L \cdot M_{p}^{(L)}} \rfloor$where N_(eCCE,k,p) and M_(p)(^(L)) may be ePDCCH resource set specific.

In another example embodiment,

${K_{{offset},p}( m^{\prime} )} = {\lfloor \frac{m^{\prime} \cdot N_{{eCCE},p,k}}{L \cdot M_{p}^{(L)}} \rfloor + \Delta_{{offset},p}}$may be used where the Δ_(offset,p) an may denote offset value for ePDCCHresource set p. For example, the first ePDCCH resource set may have azero offset value (i.e. Δ_(offset,p=0)=0) and the second ePDCCH resourceset may have a predefined value (e.g., Δ_(offset,p=1)=3). In additionalembodiments, the Δ_(offset,p) for the second set may be defined at leastone of following: the Δ_(offset,p) may be configured via higher layersignalling, Δ_(offset,p) may be implicitly configured as a function ofaggregation level and/or the number of PRBs configured for the ePDCCHresource set (i.e. the number of eCCEs N_(eCCE,k,p)), and/or theΔ_(offset,p) may be configured as a function of subframe number and/oraggregation level.

In another example, the offset (e.g., according to the ePDCCH candidatenumber and aggregation level) may be expressed asL·{(Y_(p,k)+K_(offset,p)(m′) A_(offset,p)(m′)+Δ_(offset,p)) mod└N_(eCCE,p,k)/L┘}+i where the offset(K_(offset,p)) may be defined as afunction of the ePDCCH candidate number. In this embodiment, the offsetmay be defined as

${K_{{offset},p}( m^{\prime} )} = {\lfloor \frac{m^{\prime} \cdot N_{{eCCE},p,k}}{L \cdot M_{p}^{(L)}} \rfloor.}$Additionally, the ePDCCH resource set specific offset value Δ_(offset,p)may be defined as at least one of following: the Δ_(offset,p=0)=0 forthe first ePDCCH resource set and Δ_(offset,p=1)=λ for the second ePDCCHresource set where the λ may be a predefined positive integer number(e.g., λ=3) , the Δ_(offset,p) may be configured via higher layersignalling, the Δ_(offset,p) may be implicitly configured as a functionof aggregation level and the number of PRBs configured for the ePDCCHresource set, and/or the Δ_(offset,p) may be configured as a function ofsubframe number and/or aggregation level.

According to an additional example,

${K_{{offset},p}( m^{\prime} )} = {\lfloor \frac{m \cdot N_{{eCCE},p,k}}{L \cdot M_{p}^{(L)}} \rfloor + {\Phi_{offset} \cdot n_{CI}}}$may be used (e.g., for the offset may be defined) where the Φ_(offset)may be an offset value for a cross-carrier scheduling and n_(CI) may becarrier indicator field value. The Φ_(offset) may have a differentnumber according to the ePDCCH resource set and in that case Φ_(offset)may be replaced by Φ_(offset,p). Furthermore,

${K_{{offset},p}( m^{\prime} )} = \lfloor {\frac{m \cdot N_{{eCCE},p,k}}{L \cdot M_{p}^{(L)}} + {\Phi_{offset} \cdot n_{CI}}} \rfloor$may be used. The Φ_(offset) (e.g., in such an embodiment) may be definedat least one of following: Φ_(offset) may be a predefined value andn_(CI) may be carrier indicator field value, Φ_(offset) may beconfigured via higher layer signalling, Φ_(offset) may be implicitlyconfigured as a function of an aggregation level and the number of PRBsconfigured for the ePDCCH resource set, Φ_(offset) may be configured asa function of subframe number, carrier indicator value and/oraggregation level, and/or Φ_(offset) may be defined as M_(p) ^((L))where M_(p) ^((L)) may be a number of the ePDCCH candidates for theaggregation level L in ePDCCH resource set p.

In another example,

${K_{{offset},p}( m^{\prime} )} = {\lfloor \frac{m \cdot N_{{eCCE},p,k}}{L \cdot M_{p}^{(L)}} \rfloor + {\Phi_{offset} \cdot n_{CI}} + \Delta_{{offset},p}}$may be used where the Φ_(offset) may be an offset value for across-carrier scheduling, Δ_(offset,p) may be an offset for EPDCCHresource set p, and n_(CI) may be carrier indicator field value.Alternatively,

${K_{{offset},p}( m^{\prime} )} = {\lfloor {\frac{m \cdot N_{{eCCE},p,k}}{L \cdot M_{p}^{(L)}} + {\Phi_{offset} \cdot n_{CI}}} \rfloor + \Delta_{{offset},p}}$may be used. The Φ_(offset) and Δ_(offset,p) (e.g., in such anembodiment) may be defined as least one of the following: Φ_(offset) maybe a predefined value and Δ_(offset,p) may be configured as a functionof an ePDCCH resource set index, Φ_(offset) may be a predefined valueand Δ_(offset,p) may be configured as a function of an aggregationlevel, carrier indicator value and/or aggregation levels, and/or bothΦ_(offset) and Δ_(offset,p) may be configured by higher layer signalling

In another example, the K_(offset) may be predefined as a table. Thetable 14-3 shows an example of the definition of offset value accordingto the aggregation level. The exact offset value may be different. Theexact offset value may be changed according to the system configurationand/or ePDCCH resource set configuration.

TABLE 14-3 K_(offset) according to the aggregation levels. m′ 0 1 2 3 45 Aggregation 1 0 8 16 24 32 — level: L 2 0 8 16 24 32 — 4 0 4 8 — — — 80 4 8 — — —

Alternatively, a hash function may not be used for localized ePDCCHtransmission and the ePDCCH candidates for the localized ePDCCH resourceset may be defined with at least one of the following properties: theWTRU or UE-specific search space S_(k) ^((L)) may be defined asL·{(τ+m′) mod └N_(eCCE,k)/L┘}+i where i=0, . . . , L−1,m′=m+M^((L))·n_(CI), and m=0, . . . , M^((L))−1; τ may be defined asfixed value in a predefined manner or configured via higher layersignalling in a WTRU or UE-specific manner; and/or τ may be defined as afunction of WTRU or UE-ID. For example, τ=nRNTI.

A search space may include multiple ePDCCH resource sets. The multipleePDCCH resource set may have a number of PRB-pairs that may be usedand/or the number may be fixed regardless of the system bandwidth,cell-ID, and/or subframe number or variable according to systembandwidth, cell-ID, and/or subframe number. The same number of eCCEs maybe available in ePDCCH resource sets. The number of eCCEs available inePDCCH resource set may be fixed regardless of the system bandwidth,cell-ID, and/or subframe number. The number of eCCEs available in ePDCCHresource set may be variable according to the system bandwidth, cell-ID,and/or subframe number. The number of eCCEs available in ePDCCH resourceset may be tied to the number of PRB-pairs for the ePDCCH resource setsuch as integer multiples of the number of PRB-pairs for the ePDCCHresource set. (e.g., 2 or 4 eCCEs per PRB pair may be used with 2× thenumber of PRB-pair.). Additionally, the number of eCCEs available inePDCCH resource set may be changed according to the configuration.

In another embodiment, the available number of eCCE may be differentaccording to ePDCCH resource sets. For example, the number of eCCE in anePDCCH resource set may be defined as a function of the number ofPRB-pairs configured for the ePDCCH resource set (e.g., N_(est)) and atleast one of system configurations including CP length, subframe type,duplex mode (TDD or FDD), and/or carrier type (e.g., legacy carrier orother carrier type). In this case, given that the same Nest number andCP-length may be used for an ePDCCH resource set, the larger number ofavailable eCCEs may be defined in a non-legacy carrier type as comparedwith that for legacy carrier where the non-legacy carrier type may implythat a carrier not having legacy downlink control channels and CRS inthe downlink subframes (e.g., PDCCH, PHICH, and PCFICH).

A subset of ePDCCH resource sets among the multiple ePDCCH resource setsor configured ePDCCH resource sets may be used for a WTRU or UE-specificsearch space. For example, if K_(set)=3 ePDCCH resource sets may bedefined, two ePDCCH resource sets (e.g., set 1 and 2) may be used as anePDCCH resource for a specific WTRU or UE. The multiple ePDCCH resourcesets may have at least one of the following properties

According to an example embodiment, K_(set) ePDCCH resource sets may bedefined and each ePDCCH resource set may include a same number of eCCEs(e.g., 16 eCCEs). The number of eCCEs may be fixed or variable accordingto the system parameter(s). The eCCE index may be defined from 0 to thetotal number of eCCEs in the given number of ePDCCH resource sets. Forexample, if three ePDCCH resource sets may be defined (e.g., K_(set)=3)and each ePDCCH resource set may include 16 eCCEs, the eCCE index may bedefined as (eCCE #0, . . . , eCCE #15) for the first ePDCCH resourceset, and (eCCE #16, . . . , eCCE #31) and (eCCE #32, . . . , eCCE #47)for the second and the third ePDCCH resource set, respectively. Thetotal number of eCCEs N_(eCCE) may be K_(set)·K_(eCCE) where K_(eCCE)may denote the number of eCCEs in an ePDCCH resource set,N_(eCCE)=K_(set)·K_(eCCE). The total number of eCCEs in a subframe k maybe indicated by N_(eCCE,k). In an embodiment, the WTRU or UE-specificsearch space S_(k) ^((L)) may be defined as L·{(Y_(k)+m′)mod└N_(eCCE,k)/L┘}+i, where i=0, . . . , L−1, m′=m+M^((L))·n_(CI), andm=0, . . . , M^((L))−1. Y_(k) may be defined by Y_(k)=(A·Y_(k−1)) modD,where Y⁻¹=n_(RNTI)≠0, A=39827, D=65537 and k=└n_(s)/2┘.

The eCCE index may also be defined per ePDCCH resource set. For example,if three ePDCCH sets may be defined (e.g., K_(set)=3) and each ePDCCHresource set includes 16 eCCEs, the eCCE index may be defined as (eCCE#0, . . . , eCCE #K_(eCCE−)1) for the first, second, and/or third ePDCCHresource sets. A WTRU or UE-specific search space may be defined perePDCCH resource set and the N_(eCCE,k)=K_(eCCE,k). In this case, one ormore of the following may apply. For example, the WTRU or UE specificsearch space may be defined per ePDCCH resource sets. The ePDCCHcandidates for an aggregation level may be split to two or more numberof ePDCCH resource sets. The ePDCCH resource sets may be used for theWTRU or UE-specific search spaces. A subset of ePDCCH resource sets maybe used for a specific WTRU or UE-specific search space. In anembodiment, The subset may be different according to the n_(RNTI).

Table 14-4 shows an example that two ePDCCH resource sets (e.g., n=0and 1) may be used for a WTRU or UE-specific search space and the ePDCCHcandidates may be split to two ePDCCH resource sets evenly.

TABLE 14-4 ePDCCH candidates for aggregation levels Number of ePDCCHcandidates Search space S_(k,n) ^((L)) M^((L)) Type Aggregation level Ln = 0 n = 1 WTRU or 1 3 3 UE-specific 2 3 3 4 1 1 8 1 1

The WTRU or UE specific search space S_(k,p) ^((L)) for the ePDCCHresource set p may be defined as L·{(Y_(p,k)+m′) mod └N_(eCCE,p,k)/L┘}+ior L·{(Y_(p,k)+K_(offset,p)(m′)) mod └N_(eCCE,p,k)/L┘}+i. The Y_(p,k)may be defined per ePDCCH resource sets and may have a different numberaccording to the ePDCCH resource set index p in the same subframe. The Amay be defined with a different number according to the ePDCCH resourceset index. In example embodiments, Y_(p,k) may be defined as a functionof n_(RNTI), subframe number, and/or the ePDCCH resource set index p.Additionally, Y_(p,k) may be defined by Y_(p,k)=(A_(p)·Y_(p,k−1)) modD,where Y_(p,−1)=n_(RNTI)≠0, D=65537 and k=└n_(s)/2┘. A_(p) may be definedas a prime number and when A_(p=0)=39827, the 0-th set may be the firstePDCCH resource set. A_(p), p>0 may be a prime number smaller or largerthan 39827. For example, A_(p=0)=39827 and A_(p=1)=39829 .

Additionally, Y_(p,k) may be defined byY_(p,k)=(A·Y_(p,k 1)+Δ_(offset,p))modD where the Δ_(offset,p) may beoffset for ePDCCH resource set p. In such an embodiment, theΔ_(offset,p) may be defined as at least one of following: a higher layerconfigured value; a predefined number may be used for the ePDCCHresource set specific offset, for example, the Δ_(offset,p=0)=0 and theΔ_(offset,p−1)=λ where λ may be a predefined number (e.g., 3) and/or theoffset may be randomly generated (e.g., the Δ_(offset,p=0)=0 and/or theΔ_(offset,p=1)=λ where λ may be generated as a function of a subframenumber and/or a WTRU or UE-ID (e.g., C-RNTI)) and/or the offset may bedefined as a function of one or more of the following: an ePDCCHresource type (e.g., distributed or localized), the number of PRBs, anaggregation level, an ePDCCH candidate number, and/or a number of eCCEs.

According to an example embodiment, Y_(p,k) may also be defined byY_(p,k)=(A_(p)·Y_(p,k−1)+Δ_(offset,p))modD where the Δ_(offset,p) may bean ePDCCH resource set specific offset.

The WTRU or UE-specific search space may be defined over multiple ePDCCHresource sets and the location of ePDCCH candidates for blind detectionmay be defined as a function of ePDCCH resource set number and eCCEnumber.

Additionally, an eCCE index may be defined per one or more ePDCCHresource set(s), and associated ePDCCH resource sets may be differentaccording to the ePDCCH transmission type and/or eCCE aggregationlevels. In this case, one or more of followings may be applied. Forexample, eCCE index may be defined per ePDCCH resource set in at leastone of following cases: low eCCE aggregation level may be used, such as1 and/or 2; and/or ePDCCH resource set may be configured as adistributed transmission. eCCE index may be defined over two or moreconfigured ePDCCH resource sets in at least one of following cases: higheCCE aggregation level may be used, for example, 8 or higher; and/orePDCCH resource set may be configured as a localized transmission. Oneor more subsets of the ePDCCH resource sets may be indicated from anindication channel (e.g., enhanced PCFICH) in each subframe.

For multiple ePDCCH resource sets, each ePDCCH resource set may beindependently configured as either localized or distributedtransmission. If multiple ePDCCH resource sets may be configured for aWTRU or UE, a subset of the configured ePDCCH resource sets may beconfigured to a localized transmission, and the rest of ePDCCH resourcesets may be configured for the distributed transmission: the ePDCCHcandidates may be defined in a different manner for localized anddistributed ePDCCH resource sets; a different hash function may be usedfor localized and distributed ePDCCH resource sets; and/or K_(set)ePDCCH resource sets may be defined and each ePDCCH resource set mayhave a different number of eCCEs (e.g., 16 eCCEs for the primary set and32 eCCEs for the secondary set).

When the ePDCCH candidates may be defined in a different manner forlocalized and distributed ePDCCH resource sets one or more of thefollowing may apply and/or may be used: a hash function (Y_(k)) may beused for distributed ePDCCH resource set; an offset value K_(offset) maybe used for localized ePDCCH resource set; and ePDCCH resource setdependent hash function may be used for distributed ePDCCH resourcesets. When a different hash function may be used for localized anddistributed ePDCCH resource sets, the legacy hash function may be usedfor distributed ePDCCH resource set while another hash function may bedefined for localized ePDCCH resource set.

Embodiments for antenna port mapping based on search spaces may also beprovided and/or used as described herein. For example, the same, orsimilar, ePDCCH candidates in WTRU or UE-specific search space may havea different antenna port and/or scrambling ID whereas a common searchspace may have the same antenna ports and/or scrambling ID. In suchembodiments, if a WTRU or UE-specific search space may be defined as{eCCE #n, . . . , eCCE #n+k}, a WTRU or UE behavior to monitor ePDCCHmay include one or more of the following. An antenna port for an eCCEwithin WTRU or UE-specific search space may be configured in a WTRU orUE-specific manner. For example, a WTRU or UE may demodulate eCCE #nwith antenna port-7 and another WTRU or UE may demodulate the eCCE #nwith antenna port-8. The antenna configuration may be informed to a WTRUor UE via higher layer signaling or may be implicitly derived from theRNTI. An antenna port for an eCCE within a WTRU or UE-specific searchspace may be blindly decoded within a WTRU or UE-specific search space.For example, a WTRU or UE-specific search space may include an eCCE #nwith antenna port-7 and eCCE #n with antenna port-9. The WTRU or UE mayalso demodulate (e.g., repeatedly demodulate) the same resource (eCCE#n) with antenna port-7 and antenna port-9.

According to additional embodiments, a DM-RS scrambling sequence may beprovided and/or used. For example, for the demodulation of the ePDCCH,antenna ports {7, 8, 9, 10} may be used for the channel estimation,equivalently {107, 108, 109, 110} may be used. In this case, the DM-RSsequence for the antenna ports may be defined as:

${r(m)} = {{\frac{1}{\sqrt{2}}( {1 - {2 \cdot {c( {2m} )}}} )} + {j\frac{1}{\sqrt{2}}( {1 - {2 \cdot {c( {{2m} + 1} )}}} )}}$$m = \{ {\begin{matrix}{0,1,\ldots\mspace{14mu},{{12N_{RB}^{\max,{DL}}} - {1{\mspace{11mu}\;}{for}\mspace{14mu}{normal}\mspace{14mu}{CP}}}} \\{0,1,\ldots\mspace{14mu},{{16N_{RB}^{\max,{DL}}} - {1{\mspace{11mu}\;}{for}\mspace{14mu}{extended}\mspace{14mu}{CP}}}}\end{matrix},} $where the sequence initialization c_(init) may be defined asc _(init)=(└n _(s)/2┘+1)·(2n _(ID) ^(EPDCCH)+1) ·2¹⁶ +n _(SCID)^(EPDCCH),where (n_(ID) ^(EPDCCH), n_(SCID) ^(EPDCCH)) and (X_(ID), n_(SCID)) maybe used interchangeably. For the c_(init) definition, one or more offollowings may apply: a different scrambling sequence may be used forthe same ePDCCH resource and/or a single scrambling sequence may be usedfor the ePDCCH resources in a cell.

In an embodiment, a different scrambling sequence may be used for thesame ePDCCH resource (e.g., PRB-pairs) according to the WTRU or UEand/or blind decoding attempt, for example, so that a multi-usermultiplexing gain may be increased. As an example, a WTRU or UE maydemodulate eCCE#n with a scrambling sequence and another WTRU or UE maydemodulate eCCE#n with another scrambling sequence where the scramblingsequence may be associated with a demodulation reference signal (e.g.,an antenna port). As another example, a WTRU or UE may demodulate eCCE#nwith scrambling sequence A and B. The scrambling sequence candidates maybe defined as follows: the scrambling sequence candidates may be definedwith n_(SCID) and/or X_(ID); the scrambling sequence candidates may bedefined as {n_(SCID)=0, n_(SCID)=1}; and/or scrambling sequencecandidates may be defined as {(X₁, n_(SCID)=0), (X₂, n_(SCID)=0), (X₁,n_(SCID)=1), (X₂, n_(SCID)=1)} where X₁ and X₂ may be a different numberdefined within the range of 0˜ number of cell ID.

A single scrambling sequence may also be used for the ePDCCH resourcesin a cell so that a cell specific parameter may be used for X_(ID) and afixed number may be used for n_(SCID). The X_(ID) may be defined as thephysical cell ID or configured by higher layer signaling. The n_(SCID)may be fixed as either 0 or 1.

If multiple ePDCCH resource sets may be defined, the scrambling sequencemay be used per ePDCCH resource set or across ePDCCH resource sets. Forexample, the scrambling sequence may be defined per ePDCCH resource set.Additionally, the X_(ID) may be defined per ePDCCH resource set so thatmultiple scrambling sequence may be used without a dynamic indication.In such an embodiment, when ePDCCH resource sets may be configured, theassociated X_(ID) for each ePDCCH resource set may also be configured.In this case, the n_(SCID) may be fixed as either 0 or 1. Two X_(ID) maybe configured via higher layer and each ePDCCH resource set may use oneof the X_(ID) according to the configuration. A fixed predefined X_(ID)may be used for ePDCCH candidates in common search space so that a WTRUor UE may demodulate ePDCCH candidates within common search space.Higher layer configured X_(ID) may be used for ePDCCH candidates in WTRUor UE-specific search space and the X_(ID) may be different according tothe ePDCCH resource set or the same for the ePDCCH resource sets. If twoor more of X_(ID) may be used with multiple ePDCCH resource sets, aPDSCH associated with an ePDCCH may be received in the subframe in atleast one of following manner: a WTRU or UE may use the same X_(ID) usedin the associated ePDCCH for PDSCH demodulation; and/or regardless ofthe X_(ID) used in the associated ePDCCH, a WTRU or UE may use theX_(ID) indicated by n_(SCID) in the associated DCI. If n_(SCID)=0, thenX₁ may be used. Otherwise, X₂ may be used. If the WTRU or UE may use thesame X_(ID) used in the associated ePDCCH for PDSCH demodulation, thescrambling sequence may be aligned between PDSCH and the associatedePDCCH such that the collaborative multi-point transmission (CoMP)operation may be applied for ePDCCH.

The use of X_(ID) may be dependent on the configured transmission modefor PDSCH. For example, if a WTRU or UE may be configured with non-CoMPoperation, a single X_(ID) may be used for the ePDCCH resource sets, andthe X_(ID) may be defined as physical cell ID. However, if a WTRU or UEmay be configured with CoMP operation, two or more X_(ID) may be usedand each of the ePDCCH resource sets may be configured with an X_(ID)independently. As such, X_(ID) may or may not be the same for ePDCCHresource sets.

In an additional embodiment, the DM-RS sequence may be defineddifferently according to or based on the ePDCCH search spaces. Forexample, according to the ePDCCH search space, one or more of followingmay apply and/or may be used and/or provided. In an embodiment, a WTRUor UE-specific DM-RS sequence may be configured for the WTRU orUE-specific search space and cell-specific DM-RS sequence may be usedfor the common search space. The sequence initialization c_(init) for aWTRU or UE-specific search space may be defined asc_(init)=(└n_(s)/2┘+1)·(2n_(ID) ^(EPDCCH)+1)·2¹⁶+n_(SCID) ^(EPDCCH)where n_(ID) ^(EPDCCH) may be configured via higher layer per ePDCCHresource set and n_(SCID) ^(EPDCCH) may be a fixed number (e.g., 0, 1,or 2). For the ePDCCH common search space, n_(ID) ^(EPDCCH) may bedefined as a function of the physical cell-ID and n_(ID) ^(EPDCCH) maybe a fixed number (e.g., 0, 1, or 2). For example, n_(ID) ^(EPDCCH) maybe or may be equal to the physical cell ID.

In another embodiment, both a WTRU or UE-specific search space andcommon search space may be configured with either a WTRU or UE-specificDM-RS sequence or a cell-specific DM-RS sequence.

Additionally, in an embodiment, if multiple (e.g., two) ePDCCH resourcesets may be configured for the ePDCCH WTRU or UE-specific search spaceand an (e.g., one) ePDCCH resource set may be used for the ePDCCH commonsearch space, one or more of following may apply and/or may be usedand/or provided. For example, the sequence initialization c_(init) for aWTRU or UE-specific search space may be defined in a WTRU or UE-specificmanner for each ePDCCH resource sets if the ePDCCH WTRU or UE-specificresources may not be overlapped with ePDCCH common search spaceresources. In such an embodiment, the sequence initialization c_(init)for a WTRU or UE-specific search space may be defined asc_(init)=(└n_(s)/2┘+1)·(2n_(ID) ^(EPDCCH)+1)·2¹⁶+n_(SCID) ^(EPDCCH)where n_(ID) ^(EPDCCH) may be configured via the higher layer per ePDCCHresource set and n_(SCID) ^(EPDCCH) may be a fixed number (e.g., 0, 1,or 2).

For an ePDCCH WTRU or UE-specific search space resource set that may befully and/or partially overlapped with an ePDCCH common search spaceresource, the sequence initialization c_(init) for a WTRU or UE-specificsearch space may be defined as the same as the ePDCCH common searchspace DM-RS sequence initialization. In such an embodiment, if theePDCCH common search may use a cell-specific DM-RS sequence, the WTRU orUE-specific DM-RS sequence for the ePDCCH resource set overlapped withcommon search space may use the cell-specific DM-RS sequence.Additionally, in such an embodiment, the sequence initializationc_(init) for a WTRU or UE-specific search space if the WTRU orUE-specific search space may not be overlapped with ePDCCH common searchspace may be defined as c_(init)=(└n_(s)/2┘+1)·(2n_(ID)^(EPDCCH)+1)·2¹⁶+n_(SCID) ^(EPDCCH) where n_(ID) ^(EPDCCH) may beconfigured via higher layer per ePDCCH resource set and n_(SCID)^(EPDCCH) may be a fixed number (e.g., 0, 1, or 2).

Additionally, in an example embodiment, the sequence initializationc_(init) for a WTRU or UE-specific search space if the WTRU orUE-specific search space may be overlapped with ePDCCH common searchspace may be defined as c_(init)=(└n_(s)/2┘+1). (2n_(ID)^(EPDCCH)+1)·2¹⁶+n_(SCID) ^(EPDCCH) where n_(ID) ^(EPDCCH) may bedefined as a function of the physical cell-ID and n_(SCID) ^(EPDCCH) maybe a fixed number (e.g., 0, 1, or 2). For example, n_(ID) ^(EPDCCH) maybe or may be equal to the physical cell ID.

Search space design (e.g., in CA or for multiple DL carriers) may beprovided as described herein. For example, a search space associatedwith multiple DL carriers may be implemented. In ePDCCH resources, acommon search space and WTRU or UE-specific search space may be defined.The search spaces may be defined in a multiple carrier system in one ormore of the following ways.

A common search space may be limited to being defined in PCell and/orWTRU or UE-specific search spaces may be defined in multiple componentcarriers. A WTRU or UE may limit monitoring of a common search space toPCell and WTRU or UE-specific search space in a correspondingPCell/SCell. In common search space, a carrier indication field (CIF)may indicate the corresponding component carrier in DCI format. Thecomponent carrier in which ePDCCH may be received in a WTRU orUE-specific search space may be considered as a corresponding componentcarrier. FIG. 26 illustrates an exemplary common search spacedefinition, which may be limited to legacy PDCCH region in PCell, forexample. A WTRU or UE-specific search space that may be defined in PCelland common search spaces may be defined in multiple component carriers.

Common search space may also be defined in PCell and a WTRU orUE-specific search space may be defined in at least one of SCells. Thecommon search space may be defined in legacy PDCCH in PCell and/or aWTRU or UE-specific search space may be defined in ePDCCH in at leastone of SCells.

In an embodiment, a PCell may be independently defined for legacy PDCCHand/or ePDCCH. In this case, if there may be Cell-0, Cell-1, and Cell-2,Cell-0 may be configured as PCell for legacy PDCCH and/or Cell-2 may beconfigured as PCell for ePDCCH. PCell for ePDCCH may be defined with anoffset for the PCell of legacy PDCCH.

Both WTRU or UE-specific search space and common search space may belimited to being defined in PCell. Additionally, both WTRU orUE-specific search space and common search space may be defined inmultiple component carriers.

According to an example embodiment, two ePDCCH modes may be definedand/or used such as ePDCCH frequency diversity mode (e.g., ePDCCHMode-1) and ePDCCH frequency selective mode (e.g., ePDCCH Mode-2), forexample. Additionally, the ePDCCH Mode-1 may achieve frequency diversitygain so that a common search space may be limited to being defined byePDCCH Mode-1.

In embodiments, a WTRU or UE-specific search space may be defined in oneor more of the following ways. A WTRU or UE-specific search space may bedefined by either ePDCCH Mode-1 or ePDCCH Mode-2. An ePDCCH mode for aWTRU or UE-specific search space may be configured by RRC signalling sothat a WTRU or UE may limit its monitoring to either ePDCCH Mode-1 orePDCCH Mode-2 according to the configuration. Additionally, an ePDCCHMode for WTRU or UE-specific search space may be configured according toSFN so that a WTRU or UE may know which ePDCCH Mode may be defined inthe subframe from the SFN number. In another example embodiment, anePDCCH Mode for WTRU or UE-specific search space may be configuredaccording to component carrier. For example, ePDCCH Mode-1 may beconfigured in PCell and ePDCCH Mode-2 may be configured for Secondarycell (SCell). The WTRU or UE may monitor an ePDCCH in PCell with ePDCCHMode-1 and ePDCCH Mode-2 for SCell. The ePDCCH Mode for each componentcarrier may be configured by higher layer signalling.

Furthermore, ePDCCH Mode-1 and ePDCCH Mode-2 may be defined in the samesubframe. For blind decoding, a WTRU or UE may decode half in ePDCCHMode-1 and another half in ePDCCH Mode-2. The portion of the ePDCCH Modethat the WTRU or UE may blindly decode may be different according tosubframe and/or configured by eNB. Table 15 shows an example where M₁^((L)) and M₂ ^((L)) may denote a number of ePDCCH candidates for ePDCCHMode-1 and Mode-2, respectively. A WTRU or UE may monitor one ePDCCHMode configured by an eNB via higher layer signalling.

TABLE 15 ePDCCH candidates monitored by a WTRU or UE. Number of ePDCCHSearch space S_(k) ^((L)) candidates Type Aggregation level L Size [inCCEs] M₁ ^((L)) M₂ ^((L)) WTRU 1 6 3 3 or UE- 2 12 3 3 specific 4 8 1 18 16 1 1 Common 4 16 4 8 16 2

If cross-carrier scheduling may be activated, PDCCH may be limited totransmitting in PCell such that a WTRU or UE may monitor PCell in thelimited case to receive PDCCHs. As ePDCCH may be defined, a WTRU or UEbehavior may be defined in one or more of the following ways whencross-carrier scheduling may be activated. Legacy PDCCH and/or ePDCCHmay be limited to being transmitted in PCell according to the PDCCHconfiguration. If an eNB may configure legacy PDCCH for a WTRU or UE,the WTRU or UE may be limited to monitoring legacy PDCCH in PCell.Otherwise, the WTRU or UE may monitor ePDCCH in PCell. A WTRU or UE mayassume that each PDCCH may be transmitted in PCell.

Additionally, a PCell may be defined independently for legacy PDCCH andePDCCH such as PCell_pdcch and PCell_epdcch where PCell_pdcch andPCell_epdcch denote the PCell for legacy PDCCH and ePDCCH respectively.A WTRU or UE may monitor PCell_epdcch for the set of component carriersconfigured for ePDCCH and PCell_pdcch for the other component carriersconfigured for legacy PDCCH. The PCell_pdcch and PCell_ePDCCH may be thesame component carrier.

Interference randomization may also be provided and/or used as disclosedherein. For example, a frequency location of ePDCCH may be changed fromone subframe to another to randomize interference between ePDCCHs frommultiple cells.

For such an interference randomization, a WTRU or UE may use variousbehaviors. For example, WTRU or UE behavior to monitor ePDCCH may bedefined as follows. If cross-carrier scheduling may be activated, a WTRUor UE may monitor ePDCCH in a specific cell in subframe and the indexspecific cell may be implicitly derived from SFN number and/or radioframe. If cross-carrier scheduling may not be activated, a WTRU or UEmay monitor ePDCCH in each of the configured component carriers;however, the ePDCCH resource may be changed from one subframe to anotherwithin a cell according to a SFN number and/or radio frame.

According to an example embodiment, WTRU or UE receiver processing maybe used and/or provided. For example, a PDSCH decoding processing timerelaxation may be provided. In such an embodiment, FDD (e.g., with aframe structure 1) and/or TDD (e.g., with a frame structure 2) may beprovided and/or used. For example, a TBS may be defined by the (I_(TBS),N_(PRB)) (e.g., as shown in section 7.1.7.2.1 of 3GPP TS 36.213“Physical Layer Procedures”, V10.1.0, 2011-03) and the transport blocksize may get larger as the number of (I_(TBS), N_(PRB)) becomes largerwhere 0≤I_(TBS)≤26 and 1≤N_(PRB)≤110. Since ePDCCH may be transmitted inthe PDSCH region, a WTRU or UE receiver may lose decoding processingtime for HARQ-ACK transmission which may be used to be transmitted inthe uplink subframe n+4 upon receive PDSCH in the downlink subframe n. Atiming advance (T_(TA)) may reduce PDSCH decoding processing time as itmay transmit uplink signal T_(TA) earlier where 0≤T_(TA)≤0.67[ms]. Sincelarger transport block size may use more PDSCH processing time, thelarger TBS may be restricted in the case that T_(TA) value may berelatively large and ePDCCH may be used. TBS restriction may be usedaccording to one or more of the following.

In an example method, TBS restriction may be used as follows (e.g.,according to one or more of the following). For example, I_(TBS) ^(Max)and N_(PRB) ^(Max) may be defined if I_(TBS) ^(Max)≤I_(TBS) and N_(PRB)^(Max)≤N_(PRB) where the I_(TBS) ^(Max) and N_(PRB) ^(Max) may denotethe maximum number for TBS index and number of PRBs restricted. As such,a WTRU or UE may assume that a TBS larger than (I_(TBS) ^(Max), N_(PRB)^(Max)) may not be transmitted for the WTRU or UE. The I_(TBS) ^(Max)and N_(PRB) ^(Max) may be defined in a WTRU or UE-specific manner as afunction WTRU or UE-specific timing advance value (T_(TA)). The maximumTBS (N_(TBS) ^(Max)) may also be expressed as N_(TBS) ^(Max)=Δ(I_(TBS)^(Max), N_(PRB) ^(Max)) where Δ may be a TBS table.

Additionally, the I_(TBS) ^(Max), N_(PRB) ^(Max) may be defined as afunction of timing advance value with at least one of followingequations: I_(TBS) ^(Max)=└I_(TBS)×(1−γ·T_(TA))┘ or┌I_(TBS)×(1−γ·T_(TA))┐, where the γ may be weighting factor; and/orN_(PRB) ^(Max)=└N_(PRB)×(1−δ·T_(TA))┘ or ┌N_(PRB)×(1−δ·T_(TA)┐ where theδ may be weighting factor.

The I_(TBS) ^(Max), N_(PRB) ^(Max) may further be defined as a functionof a timing advance value with at least one of following equations:I_(TBS) ^(Max)=I_(TBS)−└γ·T_(TA)┘ or I_(TBS)−┌γ·T_(TA)┐, where the γ maybe weighting factor; and/or N_(PRB) ^(Max)=N_(PRB)−└δ·T_(TA)┘ orN_(PRB)−┌δ·T_(TA)┐, where the δ may be weighting factor.

In embodiments, the N_(TBS) ^(Max) may be defined as a function of thetiming advance value with at least one of following equations: N_(TBS)^(Max)=└N_(TBS)×(1−∈·T_(TA))┘ or ┌N_(TBS)×(1−∈T_(TA))┐, where N_(TBS)may denote the largest TBS size without restriction and ∈ may be aweighting factor; and/or N_(TBS) ^(Max)=N_(TBS)−└∈·T_(TA)┘ orN_(TBS)−┌∈·T_(TA)┐.

The weighting factors γ, δ, ∈ that may be used as shown above may havefollowing characteristics: the weighting factors may be changedaccording to WTRU or UE class/category and/or the weighting factors maybe different according to transmission mode. Additionally, a maximum TBSN_(TBS) ^(Max) may be defined as a function of T_(TA) and WTRU or UEclass/category. For example, for WTRU or UE category-1, TBS restrictionmay not be used irrespective of the timing advance value.

In another example methods, a H-ARQ timing may be implemented (e.g., toallow additional decoding processing time). In a H-ARQ operation, a WTRUor UE may be requested to transmit HARQ-ACK in subframe n+k if the WTRUor UE may have received PDSCH in subframe n. In such an embodiment, kmay be set to 4 in a FDD system and k may be predefined in a TDD systembased on, for example, the UL-DL configuration and/or subframe number.Additionally, in such an embodiment, WTRU or UE behavior may be definedas follows (e.g., when a WTRU or UE may have received ePDCCH and acorresponding PDSCH in subframe n). A WTRU or UE may transmit HARQ-ACKin subframe n+l. In such an embodiment, the variable l may be set to kif a single component carrier may be activated. Additionally, thevariable l may be set to a positive integer number larger than 4 ifmultiple component carriers may be activated. The variable l may also beconfigured to a number within a set of candidates, for example, {4, 6,8, 10}, via higher layer signaling when multiple component carriers mayactivated. If a single component carrier may be activated, l may be setto k.

In an additional example method, an ePDCCH and a corresponding PDSCH maybe transmitted in a different subframe such that a WTRU or UE maymonitor ePDCCH in subframe n-i and may expect to receive a correspondingPDSCH in subframe n. In this case, a WTRU or UE behavior for a HARQ-ACKtransmission may include one or more of the following.

For example, the variable i may be either ‘0’ or a positive integer andmay be configured by higher layer signaling. In an embodiment, thevariable i may be set to ‘1’ in an FDD system. A WTRU or UE may transmitHARQ-ACK in subframe n-k irrespective of the subframe number for ePDCCHreception. The ePDCCH may be limited to transmission in subframe n-i inthe case where multiple component carriers may be activated. Otherwise,ePDCCH and the corresponding PDSCH may be transmitted in the samesubframe.

The ePDCCH may also be transmitted in subframe n-i if a timing advance(T_(TA)) for the WTRU or UE may be larger than a threshold (α). ForT_(TA)>α, a WTRU or UE may expect to receive a corresponding PDSCH insubframe n when the WTRU or UE may receive ePDCCH in subframe n-i. ForT_(TA)≤α, a WTRU or UE may receive (e.g., may expect to receive) theePDCCH and a corresponding PDSCH in the same subframe (e.g., α=0.17 ms).

Additionally, the ePDCCH may be transmitted in subframe n-i if thenumber of available downlink PRBs (e.g., associated with the systembandwidth) may be larger than the N_(PRB). The N_(PRB) may be athreshold and, in an example embodiment, N_(PRB)=50. The ePDCCH mayfurther be transmitted in subframe n-i for category 5 UEs.

One or more combinations of the above-disclosed embodiments may also beimplemented. For example, the ePDCCH may be transmitted in subframe n-iif multiple component carriers may be activated and timing advance(T_(TA)) for the WTRU or UE may be larger than threshold. The ePDCCH maybe transmitted in subframe n-i if the timing advance (T_(TA)) for theWTRU or UE may be larger than threshold and the WTRU or UE category maybe 5. The ePDCCH may be transmitted in subframe n-i if the timingadvance (T_(TA)) for the WTRU or UE may be larger than threshold and thenumber of available downlink PRBs (e.g., the system bandwidth) may belarger than N_(PRB).

TDD (e.g., frame structure 2) implementations may also be providedand/or used as described herein. For example, in TDD, the HARQ-ACKtiming may be defined according to or based on a UL-DL configurationand/or subframe number, for example, since the uplink subframe may notbe available in n+4 once a WTRU or UE may receive a PDSCH in subframe n.Table 16 shows example embodiments of HARQ-ACK timing relations bydefining k such that a WTRU or UE may transmit HARQ-ACK in uplinksubframe n+k upon detection of a PDSCH in downlink subframe n.

TABLE 16 k for TDD configurations 0-6 Subframe n The WTRU or UE may upondetection of a PDSCH in downlink TDD UL-DL subframe n transmit HARQ-ACKresponse in UL subframe n + k configuration 0 1 2 3 4 5 6 7 8 9 0  4  6U U U 4 6 U U U 1  7  6 U U 4 7 6 U U  4 2  7  6 U 4 8 7 6 U 4  8 3  411 U U U 7 6 6 5  5 4 12 11 U U 8 7 7 6 5  4 5 12 11 U 9 8 7 6 5 4 13 6 7  7 U U U 7 7 U U  5

In an embodiment, the TBS restriction may apply to the subframe with k,which may be equal to or less than K where the K value may be predefinedor configurable by higher layer signaling. As an example, if K may equalto 4, the TBS restriction may be applied for subframes 0 and 5 in UL-DLconfiguration 0 in Table 16 and it may be applied for subframe 4 inUL-DL configuration 1. In another example, if K may be equal to 5, theTBS restriction may be applied in one or more of the followingsubframes: Subframe {0, 5} in configuration 0; Subframe {4, 9} inconfiguration 1; Subframe {3, 8} in configuration 2; Subframe {0} inconfiguration 3; Subframe {8, 9} in configuration 4; Subframe {7, 8} inconfiguration 5; and/or Subframe {9} in configuration 6.

According to an additional embodiment, the TBS restriction may appliedto the subframe in which the HARQ-ACK timing may be larger than K and aWTRU or UE may have T_(TA)>α. Furthermore, from a WTRU or UE PDSCHdecoding procedure perspective, a WTRU or UE may assume that the largestTBS restriction may not be applied if HARQ-ACK timing k may be largerthan K (e.g., 4) in a subframe. As such, different WTRU or UE behaviorsmay be defined. For example, if a WTRU or UE may receive a TBS within arestricted TBS in the subframe where the HARQ-ACK timing k may be equalto or smaller than K, the WTRU or UE may assume that such a receptionmay be an error and may report DTX or NACK in the subframe n+k. If aWTRU or UE may receive a TBS within a restricted TBS in the subframewhere the HARQ-ACK timing k maybe larger than K, the WTRU or UE maystart to decode the PDSCH and report HARQ-ACK in the subframe n+k. ForTDD and FDD, the TBS restriction may apply in the downlink subframe if aWTRU or UE may report HARQ-ACK 4 ms after reception of PDSCH in thesubframe.

Embodiments may be described herein for feedback processing timerelaxation (e.g., using FDD (e.g., Frame Structure 1) and TDD (e.g.,Frame Structure 2)). As described above, aperiodic CSI feedback may beprovided and/or used. If aperiodic CSI reporting may be triggered in thedownlink subframe n, a WTRU or UE may report CSI in the uplink subframen+4. Since CSI calculation may use additional processing time, whenaperiodic CSI reporting may be triggered by ePDCCH in a downlinksubframe n, a WTRU or UE behavior may include at least one of following.

A WTRU or UE may drop CSI feedback if a PDSCH may be transmitted for theWTRU or UE in the same subframe. In this case, the dropping conditionmay be further restricted with at least one of following: the TBS forthe PDSCH in the subframe n being larger than a predefined threshold;the aperiodic CSI feedback mode using subband CQI and/or rank; thetiming advance T_(TA) being larger than a predefined threshold; theCSI-RS associated with the aperiodic CSI feedback being transmitted inthe same subframe; the system bandwidth N_(PRB) being larger than apredefined threshold (e.g., 50); and/or the like.

In an embodiment, a WTRU or UE may not assume that aperiodic CSIreporting may triggered in the subframe n via ePDCCH if a PDSCH may betransmitted in the same subframe. Such a condition may be furtherrestricted with at least one of following: the TBS for the PDSCH in thesubframe n being larger than a predefined threshold; the aperiodic CSIfeedback mode using subband CQI and/or rank; the timing advance T_(TA)being larger than a predefined threshold; the CSI-RS associated with theaperiodic CSI feedback being transmitted in the same subframe; thesystem bandwidth N_(PRB) being larger than a predefined threshold (e.g.,50); and/or the like.

Additionally, if a CSI request field in DCI format 0 and 4 may triggeraperiodic CSI reporting in subframe n, a WTRU or UE may feedback CSI insubframe n+4 in an FDD system. This WTRU or UE behavior may be provided,in an embodiment, if a WTRU or UE may receive a legacy PDCCH.

According to example embodiments, if a WTRU or UE may receive ePDCCH foraperiodic CSI reporting in a multiple carrier system, the WTRU or UEbehavior may include one or more of the following. A WTRU or UE mayreport CSI feedback in subframe n+j where: j may be set to 4 if a singlecomponent carrier may be activated; j may be set to 5 regardless of thenumber of configured component carriers (cells); j may be configured byhigher layers and j may be used when multiple component carriers may beconfigured; j may be defined according to the cell such that j may beset to 4 for PCell and j may be set to 5 for SCell and the reportingtime for PCell and SCells may be separated in the time domain; and/or jmay be set to larger than 4 when a WTRU or UE may be configuredaccording to at least one of: a timing advance (T_(TA)) for the WTRU orUE that may be larger than a threshold, aperiodic reporting triggeringbits that may indicate to report CSI for multiple component carriers,and/or if a configured PUSCH reporting mode may be based on subbandprecoding matrix indicator (PMI) reporting.

As such, WTRU or UE processing (e.g., WTRU or UE decoding processing)time relaxation in multiple carriers may be provided as describedherein. In such embodiments, a timing relations for HARQ-ACKtransmission and/or aperiodic CSI feedback may be redefined when ePDCCHmay be used, for example, in a multiple carrier system. Additionally,PDSCH decoding processing may be provided.

Uplink control channel allocation with ePDCCH may further be describedherein. For example, PUCCH resource mapping for a single DL carrier maybe provided. In such an embodiment, PUCCH resources corresponding to DLassignment messages received in an ePDCCH may be configured as afunction of RRC signaling that may be indicated to one or more WTRU(s)or UEs.

When ePDCCH reception may be enabled or configured for a WTRU or UE, atleast one or a set of candidate PUCCH resources may be assigned orindicated to a WTRU or UE. The PUCCH resources may be indicated orsignaled to one or more WTRU or UE using per-WTRU specific signaling orper-UE specific signaling, or they may be indicated or signaled to WTRUsor UEs in a cell-specific manner. A WTRU or UE following reception of aDL assignment message on ePDCCH in a DL subframe may determine thecorresponding PUCCH resource in an UL subframe as a function of theallowed or pre-configured PUCCH resources.

In another embodiment, the assigned ePDCCH resources may correspond to aset of pre-determined or configured PUCCH resources. A WTRU or UEreceiving an assignment of ePDCCH resources for decoding of DL controlinformation may obtain a corresponding PUCCH resource or a set ofallowable PUCCH resources as a function of a pre-determined mappingrelationship or table. For example, the WTRU or UE may transmit thePUCCH resource on an assigned single PUCCH resource, or in case thatmore than one PUCCH resources may be configured, assigned, or indicated,it may transmit the PUCCH on a resource selected from a set where thedetermination of the specific PUCCH resource may be subject to at leastone second determining parameter such as a signaled value part of thatDCI (e.g., ARI in TPC field for Release 10), or one or more values thatmay be derived as a function of a transmission setting like the DLassignment message mapping to the ePDCCH resources (e.g., valueassociated with antenna port number for DMRS for MU-MIMO). For a smallor well-dimensioned number of WTRUs or UEs decoding an ePDCCH, explicitconfiguration of corresponding PUCCH resources may be under control ofthe network and may provide flexibility to pool PUCCH resources whileavoiding the introduction of protocol handling in conjunction withlegacy WTRU's decoding a PDCCH.

Additionally, PUCCH resources corresponding to DL assignment messagesreceived in an ePDCCH may be derived through a dynamic resourceallocation mechanism technique as a function of one or more transmissionsetting(s) of at least one DL signal received through an ePDCCH. PUCCHresources that may be derived using a CCE index n_(CCE) on PDCCH may beextended to by CCE number definitions for ePDCCH transmissions. In suchan embodiment, PUCCH resource collision between legacy PDCCH and ePDCCHmay be avoided while re-using similar PUCCH resource allocationprinciples, such as when legacy WTRUs or UEs and ePDCCH WTRUs or UE maybe supported on a serving cell, for example.

PUCCH resource allocation with a single ePDCCH resource set may also beprovided and/or used. For example, PUCCH resources for a single ePDCCHset may be defined as described herein. In an embodiment, if either eCCEand/or eREG units in an ePDCCH may be defined similar to a legacy PDCCH,the corresponding PUCCH resource may be defined or derived as n_(PUCCH)^((1,p0))=n_(eCCE)+N_(CCE) ^(PDCCH)+N_(PUCCH), for antenna port p0, andthe PUCCH resource for antenna port p1 may be derived by n_(PUCCH)^((1,p1))=n_(eCCE)+N_(CCE) ^(PDCCH)+1+N_(PUCCH) where n_(CCE) may be thenumber of the first CCE (e.g., lowest eCCE index) used for transmissionof the corresponding PDCCH in the region of ePDCCH, N_(CCE) ^(PDCCH) maybe the total number of CCEs in the control region for the legacy PDCCH,and N_(PUCCH) ⁽¹⁾ may be configured by higher layers. In this case, oneor more of the following may be applied. N_(CCE) ^(PDCCH) may becomputed dynamically based on the detection of PCFICH (e.g., thedetection of the number of OFDM symbols) and the system bandwidth.N_(CCE) ^(PDCCH) may be set to a predefined offset value, for example,the largest CCE number of the largest system bandwidth, and may becombined with N_(PUCCH) ⁽¹⁾ such that N_(ePUCCH) ⁽¹⁾=N_(PUCCH)⁽¹⁾+N_(CCE) ^(PDCCH) may be configured by higher layers. N_(ePUCCH)⁽¹⁾=N_(PUCCH) ⁽¹⁾+N_(CCE) ^(PDCCH) may be configured by higher layersignalling such that the resource allocation may be based on n_(PUCCH)^((1,p0))=n_(eCCE)+N_(ePUCCH) ⁽¹⁾ and n_(PUCCH)^((1,p1))=n_(eCCE)+N_(ePUCCH) ⁽¹⁾+1. In this case, at least one offollowing may be applied: N_(PUCCH) ⁽¹⁾ may be configured by higherlayers and/or commonly used for PDCCH and ePDCCH (e.g., in this caseN_(CCE) ^(PDCCH) may be configured by higher layer); and/or N_(ePUCCH)⁽¹⁾ may be configured by higher layer signalling without a separateindication of N_(CCE) ^(PDCCH).

Additionally, in an embodiment, the PUCCH resource may be independent ofn_(eCCE) such that n_(ePUCCH) ^((1,p0))=N_(ePUCCH) ⁽¹⁾ and N_(ePUCCH)⁽¹⁾ may be configurable by higher layers. For a transmission mode thatmay support one or more (e.g., up to two) antenna ports, the PUCCHresource n_(PUCCH) ^((1,p1)) may be given by n_(PUCCH)^((1,p1))=N_(ePUCCH) ⁽¹⁾+1. If a WTRU or UE may be configured withMU-MIMO transmission, another determining parameter n_(MU) may be usedfor the corresponding PUCCH resource, for example, in addition ton_(eCCE) as follows: n_(PUCCH) ^((1,p0))=n_(eCCE)+N_(CCE)^(PDCCH)+N_(PUCCH) ⁽¹⁾+n_(MU) for antenna port p0 and n_(PUCCH)^((1,p1))=n_(eCCE)+N_(CCE) ^(PDCCH)+1+N_(PUCCH) ⁽¹⁾+n_(MU) for antennaport p1. In such an embodiment, n_(MU) may be determined as at least oneof following: a parameter that may be associated with an antenna portfor UE-specific DMRS; a parameter similar to ARI (ACK/NACK ResourceIndicator) configured by high layer signalling; and/or a predeterminedparameter.

In another example, PUCCH resources corresponding to DL assignments thatmay be received in an ePDCCH may be derived as a function of a CCEnumber. For example, a first or pre-determined CCE or equivalent mappingunit in an ordered sequence may be obtained from decoding a DLassignment message that may be mapped in a time and/or frequencyresource grid.

Additionally, the sequence of mapping units such as eCCEs or eREGs thatmay be chosen to dynamically derive or determine the PUCCH resourceselection in the WTRU or UE decoding ePDCCH may or may not be in arelationship with the CCE sequence and starting CCE indices that may beused in conjunction with dynamic PUCCH resource allocation used whendecoding PDCCH. A WTRU or UE decoding ePDCCH determining its PUCCHresource may compute the UL transmission setting both from a firstdynamically computed transmission setting such as a starting (e)CCE orequivalent and one or more pre-configured or signaled parameters asdescribed herein.

According to an example embodiment, PUCCH resources that may be used inconjunction with PDCCH (e.g., if present) and ePDCCH may be segmented oraggregated for WTRUs assigned to decode one of these by the network. Ina setup, PUCCH resources may be pooled, for example, UL RBs for a legacyWTRU's or UE's decoding of PDCCH and a WTRU's or UE's decoding ofePDCCH. In some additional embodiments (e.g., when trying to achievespatial multiplexing gains), segregated UL resources may be chosen for aWTRU's decoding of legacy PDCCH versus those that may decode ePDCCH.

In the foregoing examples, when introducing (e)CCE and/or (e)REG units,groups or units of REs may not imply or know that they may be the sameas the CCEs that include 9 REGs or REGs that include 4 REs used on aPDCCH. Additionally, an ordered sequence of mapping units correspondingto the time and/or frequency resource allocation for one or moreePDCCH(s) may be equivalent in the described embodiments. In anembodiment, PUCCH resources for a WTRU's or UE's decoding of at leastone ePDCCH and which may be configured to receive more than one DLserving cell may be derived through RRC signalling to one or more WTRUsor UEs.

Embodiments may also be described herein for PUCCH resource allocationwith multiple ePDCCH resource sets. For example, if either eCCE or eREGunits in an ePDCCH set may be defined similarly to a legacy PDCCH, thecorresponding PUCCH resources for a UE may be derived as n_(PUCCH)^((1,p0))=n_(eCCE)+N_(eCCE_Offset) ^((ePDCCHN_Set))+N_(PUCCH) ⁽¹⁾, forantenna port p0 and/or the PUCCH resource for antenna port p1 may bederived by n_(PUCCH) ^((1,p1))=n_(cCCE)+N_(eCCE_Offset)^((ePDCCH_Set))+1+N_(PUCCH) ⁽¹⁾ where n_(eCCE) may be the number of thefirst eCCE (e.g., the lowest eCCE index that may be used to constructthe PDCCH) that may be used for transmission of the corresponding PDCCHin the region of an ePDCCH set configured for a UE, N_(eCCE_Offset)^((ePDCCH_Set)) may be the PUCCH resource offset for an ePDCCH set,and/or N_(PUCCH) ⁽¹⁾ may be configured by higher layers. In thisembodiment, one or more of following may apply: N_(eCCE_Offset)^((ePDCCH_Set)) may be computed dynamically based on the detection ofPCFICH (e.g., the detection of the number of OFDM symbols) and thesystem bandwidth; N_(eCCE_Offset) ^((ePDCCH_Set)) may be set to apredefined offset value, for example, the largest CCE number of thelargest system bandwidth, and/or be combined with N_(PUCCH) ⁽¹⁾ so thatN_(ePUCCH) ⁽¹⁾=N_(PUCCH) ⁽¹⁾+N_(eCCE_Offset) ^((ePDCCH_Set)) may beconfigured by higher layers; and/or N_(ePUCCH) ⁽¹⁾=N_(PUCCH)⁽¹⁾+N_(eCCE_ Offset) ^((ePDCCH Set)) may be configured by higher layersignalling, resulting resource allocation may be based on n_(PUCCH)^((1,p0))=n_(eCCE)+N_(ePUCCH) ⁽¹⁾ and n_(PUCCH)^((1,p1))=n_(eCCE)+N_(ePUCCH) ⁽¹⁾+1. In this last embodiment, at leastone of following may be applied: N_(PUCCH) ⁽¹⁾ may be configured byhigher layers and/or used for PDCCH and ePDCCH (e.g., in this caseN_(eCCE_Offset) ^((ePDCCH_Set)) may be configured by higher layers);N_(ePUCCH) ⁽¹⁾ may be configured by higher layer signalling without aseparate indication of N_(CCE) ^(PDCCH); and/or N_(ePUCCH) ⁽¹⁾ may beconfigured per set independently, which may be defined as N_(ePUCCH)^((1),ePDCCH_Set).

Multiple N_(ePUCCH) ^((1), k) where k=0,1 , . . . , K−1 may also beconfigured and/or indicated via dynamic signalling. For example, thePUCCH resource allocation based on ePDCCH may be defined as n_(PUCCH)^((1,p0))=n_(eCCE)+N_(ePUCCH) ^((1),k). In this case, one or more offollowings may apply. The k may be indicated dynamically by a DCIassociated with PDSCH transmission in the subframe. For example, a bitfield may indicate the value of k so that a UE may derive the PUCCHresource. Additionally, ARI in a DCI may be reused to indicate k. AScrambling ID (e.g., nSCID) for the DCI may also implicitly indicate k.The K may be the same as the number of ePDCCH resource sets that may beconfigured and/or each k may be one-to-one mapped with the configuredePDCCH resource set. The K may also be defined as 2 or 4 and/or, if asingle ePDCCH resource set may be configured, K=1.

In an alternative or additional embodiment, N_(eCCE_Offset)^((ePDCCH_Set)) may be combined with N_(PUCCH) ⁽¹⁾ where, for example,N_(ePUCCH) ⁽¹⁾=N_(PUCCH) ⁽¹⁾+N_(CCE) ^(PDCCH), and N_(ePUCCH) ⁽¹⁾ may besignaled dynamically and/or configured semi-statically or by higherlayers. If a WTRU or UE may be configured with a MU-MIMO transmission,another (e.g., second) determining parameter n_(MU) may be used for thecorresponding PUCCH resource in addition to n_(eCCE) as follows:n_(PUCCH) ^((1,p0))=n_(eCCE)+N_(eCCE_Offset) ^((ePDCCH_Set))+N_(PUCCH)⁽¹⁾+n_(MU) for antenna port p0 and n_(PUCCH)^((1,p1))=n_(eCCE)+N_(eCCE_Offset) ^((ePDCCH_Set))+1+N_(PUCCH)⁽¹⁾+n_(MU) for antenna port p1 where n_(MU) may be determined as atleast one of following: parameter associated with antenna port forUE-specific DMRS; parameter similar to ARI configured by high layersignalling; and/or parameter predetermined.

PUCCH resource mapping for multiple DL carriers may also be providedand/or used as described herein. For example, when ePDCCH reception maybe enabled or configured for a WTRU or UE and a WTRU or UE may beconfigured to receive more than one DL serving cell, the PUCCH resourcecorresponding to a first DL assignment message received on a firstePDCCH may be derived by the WTRU or UE as a function of a second DLassignment message received on a second DL control channel.

Additionally, in an embodiment, a WTRU or UE may decode a legacy PDCCHon a Primary (DL) serving cell while decoding ePDCCH on a Secondary (DL)serving cell. The PUCCH resource to be used may be determined by theWTRU or UE as a function of the DL assignment message received on thePrimary serving cell. In the case of 2 DL serving cells, the derivedPUCCH format 1 with channel selection resources may be obtained from theDL assignment message on the Primary Cell. In the case of PUCCH format3, the WTRU or UE may select a PUCCH resource from the set ofpre-configured RRC signaled parameters through use of a signaledresource selector, e.g., ARI carried in the DL assignment message on(e)PDCCH on a Secondary serving cell.

The WTRU or UE may also decode ePDCCH on both the Primary and aSecondary serving cell. In such an embodiment, the PUCCH resource to beused may be determined by the WTRU or UE as a function of a firstePDCCH, and may be used to transmit UL control information like A/Ncorresponding to one or more received DL assignments on these ePDCCHs.In the case of 2 DL serving cells, the derived PUCCH format 1 withchannel selection resources may be obtained from the DL assignmentmessage on the Primary Cell.

Embodiments may also be described herein for PUCCH resource allocationwith a single ePDCCH resource set. For example, if eCCE and/or eREGunits in an ePDCCH may be defined similar to a legacy PDCCH, thecorresponding PUCCH resource may be defined or derived as n_(PUCCH,j)⁽¹⁾=n_(eCCE)+N_(CCE) ^(PDCCH)+N_(PUCCH) ⁽¹⁾, and for a transmission modethat supports up to two transport blocks, the PUCCH resourcen_(PUCCH,j−1) ⁽¹⁾ may be defined or derived by n_(PUCCH,j+1)⁽¹⁾=n_(eCCE)+N_(CCE) ^(PDCCH)+1+N_(PUCCH) ⁽¹⁾ where n_(eCCE) may be thenumber of the first eCCE (e.g., the lowest eCCE index used to constructthe PDCCH) used for transmission of the corresponding PDCCH in theregion of ePDCCH, N_(CCE) ^(PDCCH) may be the total number of CCEs inthe control region for the legacy PDCCH and N_(PUCCH) ⁽¹⁾ may beconfigured by higher layers. N_(CCE) ^(PDCCH) may be computeddynamically based on the detection of PCFICH (e.g., the detection of thenumber of OFDM symbols) and the system bandwidth. N_(CCE) ^(PDCCH) maybe set to a predefined offset value, for example the largest CCE numberof the largest system bandwidth, and may be combined with N_(PUCCH) ⁽¹⁾so that N_(PUCCH) ⁽¹⁾=N_(PUCCH) ⁽¹⁾+N_(CCE) ^(PDCCH) may be configuredby higher layers.

In embodiment, the PUCCH resource may be independent of n_(eCCE) suchthat n_(PUCCH,j) ⁽¹⁾=N_(ePUCCH) ⁽¹⁾ and N_(ePUCCH) ⁽¹⁾ may beconfigurable by higher layers. For a transmission mode that supports upto two transport blocks, the PUCCH resource n_(PUCCH,j+1) ⁽¹⁾ may begiven by n_(PUCCH,j+1) ⁽¹⁾=N_(ePUCCH) ⁽¹⁾+1.

Additionally, if a WTRU or UE may be configured with MU-MIMOtransmission, the corresponding PUCCH resources may be derived asn_(PUCCH,j) ⁽¹⁾=n_(eCCE)+N_(CCE) ^(PDCCH)+N_(PUCCH) ⁽¹⁾+n_(MU), and fortransmission mode that supports multiple (e.g., up to two) transportblocks, the PUCCH resource n_(PUCCH,j+1) ⁽¹⁾ may be derived byn_(PUCCH,j+1) ⁽¹⁾=n_(eCCE)+N_(CCE) ^(PDCCH)+1+N_(PUCCH) ⁽¹⁾+n_(MU) wheren_(MU) may be determined as at least one of following: a parameter thatmay be associated with antenna port for UE-specific DMRS; a parameterthat may be similar to ARI configured by high layer signaling; aparameter that may be similar to ARI carried in TPC field of the DLassignment message on (e)PDCCH on a secondary serving cell (e.g., as forRel-10); and/or a predetermined parameter.

In PUCCH resource allocation with multiple ePDCCH resource sets, thePUCCH resources for multiple ePDCCH sets may be defined as follows. Ifeither eCCE or eREG units in an ePDCCH set may be defined similarly to alegacy PDCCH, the corresponding PUCCH resources for a UE may be derivedas n_(PUCCH,j) ⁽¹⁾=n_(eCCE)+N_(eCCE_Offset) ^((ePDCCH_Set))+N_(PUCCH)⁽¹⁾, and for transmission mode that supports up to two transport blocks,the PUCCH resource n_(PUCCH,j+1) ⁽¹⁾ may be derived by n_(PUCCH,j+1)⁽¹⁾=n_(eCCE)+N_(eCCE_Offset) ^((ePDCCH_Set))+1+N_(PUCCH) ⁽¹⁾ wheren_(eCCE) may be the number of the first eCCE (e.g., the lowest eCCEindex used to construct the PDCCH) used for transmission of thecorresponding PDCCH in the region of an ePDCCH set configured for a UE,N_(eCCE_Offset) ^((ePDCCH_Set)) may be the PUCCH resource offset for anePDCCH set, and N_(PUCCH) ⁽¹⁾ may be configured by higher layers.N_(eCCE_Offset) ^(ePDCCH_Set)) may be signaled dynamically or configuredsemi-statically. N_(eCCE_Offset) ^((ePDCCH_Set)) may be combined withN_(PUCCH) ⁽¹⁾, i.e. N_(ePUCCH) ⁽¹⁾=N_(PUCCH) ⁽¹⁾+N_(CCE) ^(PDCCH),N_(ePUCCH) ⁽¹⁾ may be signaled dynamically, or configuredsemi-statically or by higher layers. If a WTRU or UE may be configuredwith a MU-MIMO transmission, the corresponding PUCCH resources may bederived as n_(PUCCH,j) ⁽¹⁾=n_(eCCE)+N_(eCCE_Offset)^((ePDCCH_Set))+N_(PUCCH) ⁽¹⁾+n_(MU), and for transmission mode thatsupports up to two transport blocks, the PUCCH resource n_(PUCCH,j+1)⁽¹⁾ may be derived by n_(PUCCH,j+1) ⁽¹⁾=n_(eCCE)+N_(eCCE_Offset)^((ePDCCH_Set))+1+N_(PUCCH) ⁽¹⁾+n_(MU) where n_(MU) may be determined asat least one of following: a parameter associated with antenna port forUE-specific DMRS; a parameter similar to ARI configured by high layersignaling; a parameter similar to ARI carried in TPC field of the DLassignment message on (e)PDCCH on a Secondary serving cell (e.g., as forRel-10); and/or a predetermined parameter.

In the case of PUCCH format 3, the WTRU or UE may select a PUCCHresource from the set of pre-configured RRC signaled parameters throughuse of a signaled resource selector, for example, an ARI carried in theDL assignment message on (e)PDCCH via a Secondary serving cell.

Based on the foregoing, in the single carrier case for the use ofexplicitly configured, or implicitly derived PUCCH resources, or both ofthem in a combination, PUCCH format 3 may be used for the case ofmultiple DL serving cells, e.g., carrier aggregation with a Primary DLserving cell and at least one Secondary cell.

A PDSCH transmission mode associated with ePDCCH may further be providedand/or used described herein. For example, for a PDSCH transmission,several transmission modes may be available in a system to supportvarious channel/system environments such as closed-loop spatialmultiplexing mode, open-loop spatial multiplexing mode, transmitdiversity, and/or single antenna port mode. The transmission mode may beconfigured via higher layer signaling, for example, so that an eNBscheduler may choose an adequate transmission mode for PDSCHtransmission. Table 3 shows the transmission modes supported inLTE/LTE-A. The transmission modes using antenna port 7˜10 for the PDSCHdemodulation may use the ePDCCH. If a WTRU or UE may be configured witha specific transmission mode, such as transmission mode 2, which may useCRS for the PDSCH demodulation, the WTRU or UE may monitor legacy PDCCHfor the PDSCH reception. If a WTRU or UE may be configured to monitorePDCCH while the configured transmission mode for PDSCH may be 2 (e.g.,transmit diversity mode), the WTRU or UE may monitor legacy PDCCH toreceive DCI associated with PDSCH in the subframes. If a WTRU or UE maybe configured to monitor ePDCCH while the configured transmission modefor PDSCH may be 9, the WTRU or UE may monitor ePDCCH to receive DCI inWTRU or UE-specific search space in the subframes configured for ePDCCHreception.

Additionally, ePDCCH may be used irrespective of the transmission modeconfigured for PDSCH transmission. For example, the transmission modesor CQI reporting modes configured for the WTRU or UE may be implicitlytied with a type of ePDCCH transmission. According to the configuredtransmission mode, the supportable ePDCCH transmission type may bedifferent. For example, if a WTRU or UE may be configured with open-looptransmission modes such as transmit diversity (e.g., TM mode-2) oropen-loop spatial multiplexing mode (e.g., TM mode-3), the WTRU or UEmay assume that ePDCCH resource sets configured for the WTRU or UE maybe used as distributed transmission. The open-loop transmission modesfor PDSCH may be associated with ePDCCH distributed transmission. Theclosed transmission modes for PDSCH may be associated with ePDCCHlocalized transmission. According to the configured CQI reporting modes,the supportable ePDCCH transmission type may be different. For example,if a WTRU or UE may be configured with a reporting mode which uses PMIand CQI report, the WTRU or UE may assume that the ePDCCH resource setsconfigured for the WTRU or UE may be used as localized transmission. Ifa WTRU or UE may be configured with wideband CQI reporting in PUSCHreporting mode, the WTRU or UE may assume that the ePDCCH resource setsconfigured for the WTRU or UE may be for distributed transmission.Otherwise, the WTRU or UE may assume that the ePDCCH resource setsconfigured for the WTRU or UE may be for localized transmission or both.If a WTRU or UE may be configured for CoMP transmission mode, the WTRUor UE may also assume that the ePDCCH resource sets configured for theWTRU or UE may be defined as localized transmission.

Systems and/or methods may be provided herein for ePDCCH reception. Forexample, a WTRU or UE may be configured with ePDCCH or legacy PDCCH andthe WTRU or UE behavior to receive the ePDCCH may be as follows. A WTRUor UE may receive ePDCCH configuration information in broadcastinformation. For example, MIB or SIBs may include an ePDCCHconfiguration so that a WTRU or UE may know the ePDCCH resources beforeRACH procedures. To receive broadcast information such as SIBs, a WTRUor UE may decode SI-RNTI in legacy PDCCH. A WTRU or UE may be configuredto receive legacy PDCCH and/or ePDCCH during RACH procedures. Forcontention-based RACH procedures, a WTRU or UE may receive PDCCHconfiguration information in either msg2 or msg4, which may betransmitted from an eNB. For non-contention-based RACH procedures, aWTRU or UE may receive PDCCH configuration information inhandover/mobility information or msg2 which may be transmitted from eNB.When a WTRU or UE may be configured to a specific PDCCH type, the WTRUor UE may blind decode DCIs in the configured PDCCH region (e.g., legacyPDCCH or ePDCCH). When a WTRU or UE may be configured to a specificPDCCH type, the WTRU or UE may blind decode a common search space in alegacy PDCCH region and a WTRU or UE-specific search space in an ePDCCHregion.

In embodiments, systems and/or methods for PDCCH fallback transmissionmay also be disclosed. For example, as an ePDCCH may be definedadditionally on top of a legacy PDCCH, an eNB may configure a legacyPDCCH or ePDCCH in a WTRU or UE-specific manner to utilize PDCCHresources. If the PDCCH resources may be configured by higher layersignaling, there may be an ambiguity period in which the eNB may notknow whether the WTRU or UE may be monitoring the legacy PDCCH or theePDCCH. In order for the WTRU or UE to receive the PDCCH regardless ofthe PDCCH configuration, at least one of following can be used.

An eNB may transmit both a legacy PDCCH and an ePDCCH in the samesubframe for ambiguity periods and may be detect which PDCCH resourcethe WTRU or UE may be monitoring for from DTX of HARQ-ACK. A PUCCHresource for the legacy PDCCH and the ePDCCH may be definedindependently.

A common search space may be defined in the legacy PDCCH, and a fallbacktransmission mode (e.g., DCI format 1A) may be used for ambiguityperiods. The PDCCH resource configuration may indicate the legacy PDCCHor the ePDCCH regarding the WTRU or UE-specific search space. Forexample, in an embodiment, a fall-back PDCCH resource may be defined ina broadcast channel. A common search space may be defined in legacyPDCCH or ePDCCH via a broadcast channel (e.g., SIB-x) and the commonsearch space may not be changed according to the PDCCH configuration.

Additionally, the PDCCH type may be configured by legacy PDCCH or ePDCCHwith an activation timer. If a WTRU or UE monitors the legacy PDCCH, atriggering PDCCH based on the legacy PDCCH may be used to inform a WTRUor UE to monitor the ePDCCH from subframe n+x when the triggering PDCCHmay be received in subframe n where x may be predefined or configured.If a WTRU or UE monitors the ePDCCH, a triggering ePDCCH based on theePDCCH may be used to inform a WTRU or UE to monitor the legacy PDCCHfrom subframe n+x when the triggering ePDCCH may be received in subframen, where x may be predefined or configured.

A MAC CE with activation and/or deactivation command may be used toconfigure PDCCH type according to an embodiment. For example, anactivation and/or deactivation command may be transmitted with a timersuch as x so that if a WTRU or UE receives MAC CE in subframe n, thecommand may be activated and/or deactivated in subframe n+x where x maybe predefined or configured.

According to example embodiments, if multiple component carriers may beconfigured, at least one of following may be used to handle ambiguityperiods. For example, a common search space may be defined in the legacyPDCCH of a Pcell and cross-carrier scheduling may be activated.Additionally, cross-carrier scheduling may be activated for commonsearch space and available in a legacy PDCCH region. A WTRU orUE-specific search space may also be defined in a legacy PDCCH and/or anePDCCH (e.g., with or without cross-carrier scheduling).

Embodiments may also be described herein for handling of or avoidingcollision with other signals. ePDCCH RBs may be the same as RBs in whichePDCCH candidate(s) may be located. Although described in the case ofcollision between ePDCCH and PRS, the described embodiments may applyfor other cases, for example, if ePDCCH resources may collide with othersignals including other reference signals, or broadcasting channels.Although described for handling of or avoiding collision with othersignals, the described embodiments may apply for other cases, forexample, to restrict or otherwise limit ePDCCH to or from certainresource elements (REs), RBs, or subframes for any reason.

WTRU or UE reception of PRS information may be provided and/or used inan embodiment. For example, the WTRU or UE may receive PRS informationfor a cell for a reason other than positioning such as for a cell forwhich it may read ePDCCH or for which it may be configured for ePDCCH.The WTRU or UE may receive this information from the eNB, for example,via RRC signalling which may be dedicated or broadcast signalling. TheWTRU or UE may receive this information included with an ePDCCHconfiguration which may be received in dedicated or broadcastsignalling. The certain cell for which, and/or from which, the WTRU orUE may receive this information may be a serving cell of the WTRU or UE,such as a primary serving cell (PCell) or a secondary serving cell(SCell), for example. The WTRU or UE may also receive this informationfor a neighbor cell, as part of mobility information, or as part ofconfiguration related to a handover to another serving cell.

In an example embodiment, the information the WTRU or UE may receive fora given cell may include one or more of the subframes the PRS may betransmitted in, a PRS configuration index, a number of DL subframes, aBW for PRS transmission, PRS muting information, a PRS period, a PRSoffset, a PRS muting period, a PRS muting sequence (e.g., which PRSoccasions may be muted in each PRS muting period), and/or an indicationas to whether or not the cell transmits PRS. For the PRS mutingsequence, which may be included as part of the PRS muting information,if a p-bit field may be used to represent a muting sequence with aperiod p, the first bit of the field may correspond to the first PRSpositioning occasion that may start after the beginning of SFN=0 of thecell for which the PRS muting sequence may be received by the WTRU orUE.

eNB scheduling may be used or performed in an embodiment. For example,the eNB may schedule and/or transmit ePDCCH in such a way as to avoidcollision of ePDCCH RBs and PRS RBs or to reduce the impact of thecollision. In subframes in which the eNB may transmit PRS in a givencell, the eNB may not schedule or may not transmit ePDCCH in any RBs ofthat cell. In subframes in which the eNB may transmit PRS in a givencell, the eNB may not schedule or may not transmit ePDCCH in RBs thatoverlap the PRS BW in that cell, for example, in RBs that may collidewith PRS RBs in that cell. The eNB may configure ePDCCH in a given cellin such a way that it may not collide with PRS in subframes in which theeNB may transmit PRS in that cell. This may be applicable for the casein which the PRS BW may not be the full DL BW of the cell, for example.

Whether or not an eNB may schedule or transmit ePDCCH in certainsubframes or certain RBs may be based on whether, or how much, theePDCCH DM-RS REs may collide with PRS REs. For example, if in a givensubframe in which the eNB may transmit PRS, one or more ePDCCH RBs maycollide with PRS RBs, then one or more of the following may apply: theeNB may transmit ePDCCH in that subframe or in the colliding RBs if inthe colliding RBs, the ePDCCH DM-RS REs may not collide with PRS REs;the eNB may not transmit ePDCCH in that subframe or in the colliding RBsif in the colliding RBs, at least one ePDCCH DM-RS RE may collide with aPRS RE; the eNB may not transmit ePDCCH in that subframe or in thecolliding RBs if in the colliding RBs, certain ePDCCH DM-RS REs collidewith PRS REs; the eNB may not transmit ePDCCH in that subframe or in thecolliding RBs if in the colliding RBs, at least a certain number ofePDCCH DM-RS REs collide with PRS REs; the eNB may not transmit ePDCCHin that subframe or in the colliding RBs if due to the collision ofePDCCH REs and PRS REs in the colliding RBs certain or at least acertain number of antenna ports become unavailable for use in those RBswhich may be due to the collision of one or more ePDCCH REs and PRS REs;and/or the like.

Embodiments may be described herein for WTRU or UE reception of ePDCCH,for example, for collision handling. The WTRU may determine whether ornot to monitor or attempt to decode ePDCCH candidates in certainsubframes or RBs of a cell based on at least one or more PRS parametersor transmission characteristics for that cell. The WTRU or UE may takeinto account the subframes in which the PRS may be transmitted. Forexample, in subframes in which PRS may be transmitted, the WTRU or UEmay monitor or attempt to decode PDCCH candidate(s) in those subframesand may not (or may be permitted to not) monitor or attempt to decodeePDCCH candidate(s) in those subframes.

In an embodiment, the WTRU or UE may take into account the subframes andthe RBs in which ePDCCH and/or PRS may be transmitted. For example, insubframes in which PRS may be transmitted, the WTRU or UE may not (ormay be permitted to not) monitor or attempt to decode ePDCCHcandidate(s) in those subframes if the ePDCCH candidate(s) may belocated in RBs that may collide with PRS RBs. In subframes in which PRSmay be transmitted, the WTRU or UE may not (or may be permitted to not)perform one or more of the following: monitor or attempt to decodeePDCCH candidate(s) in those subframes if at least one of the ePDCCHcandidates may be located in RBs that may collide with PRS RBs; monitoror attempt to decode ePDCCH candidate(s) in those subframes if more thana certain number of ePDCCH candidate(s) may be located in RBs that maycollide with PRS RBs; monitor or attempt to decode ePDCCH candidate(s)in those subframes if the ePDCCH candidate(s) (e.g., each or all ofthem) in those subframes may be located in RBs that may collide with PRSRBs; monitor or attempt to decode ePDCCH candidate(s) located in RBsthat may collide with PRS RBs; and/or the like. In subframes in whichPRS may be transmitted, the WTRU may (or may be required to) monitor orattempt to decode one or more of the following: ePDCCH candidate(s)located in RBs that may not collide with PRS RBs in that cell and/orcertain (e.g., each or all) ePDCCH candidates if no ePDCCH candidate(s)may be located in RBs that may collide with PRS RBs (e.g., if there maynot be overlap between the RBs in which the ePDCCH candidate(s) may belocated and the PRS BW).

Additionally, the WTRU or UE may take into account the subframes and theREs in which PRS may be transmitted and may take into account whether,or how much, the PRS REs may collide with ePDCCH DM-RS REs, for example.In subframes in which PRS may be transmitted, the WTRU or UE may (or maybe required to) monitor or attempt to decode ePDCCH candidate(s) locatedin RBs that may collide with PRS RBs if, in the colliding RBs, none ofthe ePDCCH DM-RS REs may collide with PRS REs; and/or may not (or may bepermitted to not) monitor or attempt to decode ePDCCH candidate(s)located in RBs that may collide with PRS RBs if, in the colliding RBs,at least one ePDCCH DM-RS RE may collide with a PRS RE; and/or may not(or may be permitted to not) monitor or attempt to decode ePDCCHcandidate(s) located in RBs that may collide with PRS RBs if, in thecolliding RBs, certain ePDCCH DM-RS REs may collide with PRS REs; and/ormay not (or may be permitted to not) monitor or attempt to decode ePDCCHcandidate(s) located in RBs that may collide with PRS RBs if, in thecolliding RBs, at least a certain number of ePDCCH DM-RS REs may collidewith PRS REs; and/or may not (or may be permitted to not) monitor orattempt to decode ePDCCH candidate(s) located in RBs that may collidewith PRS RBs if, in the colliding RBs, certain or at least a certainnumber of antenna ports may become unavailable for use in those RBswhich may be due to the collision of one or more ePDCCH REs and PRS REs;and/or the like.

In subframes in which PRS may be transmitted in a given cell, the WTRUor UE may determine which ePDCCH candidate(s) it may (or may be requiredto) or may not (or may be permitted to not) monitor or attempt to decodebased on at least one of the physical layer cell ID, the value of thePRS v_(shift) value which may be defined as v_(shift)=N_(ID) ^(cell)mod6, where N_(ID) ^(cell) may be the physical layer cell identity, orthe cyclic prefix (CP length) of the subframe or cell, for example, thatmay be normal or extended. One or more of these parameters may be usedby the WTRU to determine the location of the PRS REs which the WTRU orUE may use to determine which ePDCCH DM-RS REs may collide with PRS REs.

In subframes in which PRS may be transmitted in a given cell, the WTRUor UE may determine which ePDCCH candidate(s) it may(or may be requiredto) or may not (or may be permitted to not) monitor or attempt to decodebased on at least the number of antenna ports configured for ePDCCH inthat cell. If the antenna ports may be restricted in certain subframes,the WTRU may use the ports after the restriction instead of theconfigured ports in those subframes for the determination. For example,antenna ports {7, 8, 9, 10} may be used in regular subframes whileantenna ports {7, 8} or {9, 10} may be used in certain subframes.

In another embodiment, a search space fallback may be implemented orused. For example, for WTRUs configured for ePDCCH, PDCCH may includecommon search space. In certain subframes such as subframes in which PRSmay be transmitted, PDCCH may include a WTRU or UE-specific search spacefor WTRUs or UEs configured for ePDCCH. If in a subframe a WTRU or UEconfigured for ePDCCH may not (or may be permitted to not) monitor orattempt to decode ePDCCH candidate(s), for example in accordance withone of the solutions described herein, the WTRU or UE may (or may berequired to) monitor or attempt to decode common search space and/orWTRU or UE-specific search space in the PDCCH region.

For example, a WTRU or UE configured for ePDCCH may fall back to monitoror attempt to decode PDCCH candidate(s) which may be defined within aWTRU or UE-specific search space in a PDCCH region. Fall back may beprovided or used in subframes in which PRS may be transmitted in a celland/or may be based on at least one of PRS information (e.g., one ormore of the information items described herein), PRS transmissionparameters, physical layer cell ID, CP length in the cell or subframe(e.g., normal or extended), number of antenna ports configured forePDCCH transmission, antenna port restrictions, and/or the like.

Certain subframes may be configured as fallback subframes. The eNB mayprovide such a configuration to the WTRU or UE. According to exampleembodiments, such a configuration may be received by the WTRU or UE fromthe eNB via broadcast or dedicated signaling such as RRC signaling.

In subframes which may be configured as fallback subframes, a WTRU or UEconfigured for ePDCCH may not (or may be permitted to not) monitor orattempt to decode ePDCCH candidate(s). In subframes which may beconfigured as fallback subframes, for a certain WTRU or UE, such as aWTRU or UE configured for ePDCCH, WTRU or UE-specific search space forthe WTRU or UE may be defined in a PDCCH region. In subframes such asthese subframes, the WTRU or UE may (or may be required to) monitor orattempt to decode PDCCH candidate(s), such as common search space PDCCHcandidates and/or WTRU or UE-specific search space PDCCH candidates, ina PDCCH region. In subframes which may not be configured as fallbacksubframes, a certain WTRU or UE, such as a WTRU or UE configured forePDCCH, may (or may be required to) monitor or attempt to decode ePDCCHcandidates in a PDSCH region. The fallback subframe may be configuredwith at least one of a period, an offset, a number of subframesconsecutively configured (e.g., number of consecutive DL subframes),and/or other parameters.

Additionally, configuration of ePDCCH subframes or ePDCCH monitoringsubframes may be equivalent to configuration of fallback subframes whereePDCCH subframes or ePDCCH monitoring subframes may be treated in anopposite manner from fallback subframes. For example, the WTRU or UEand/or eNB may treat subframes which may not be configured as ePDCCHsubframes or ePDCCH monitoring subframes in the manner described hereinfor subframes which may be configured as fallback subframes. The WTRU orUE and/or the eNB may treat subframes which may be configured as ePDCCHsubframes or ePDCCH monitoring subframes in the manner described hereinfor subframes which may not be configured as fallback subframes.

Embodiments may be described herein for handling PRS REs. In subframesin which PRS may be transmitted, for ePDCCH candidate(s) which may belocated in RBs that the WTRU or UE may attempt to decode, the WTRU or UEmay assume that for the REs which may contain data (e.g., REs which maynot contain CRS or DM-RS or CSI-RS), ePDCCH may not be transmitted inREs that may collide with PRS REs. The WTRU or UE may assume that ePDCCHREs are rate-matched around for those REs accordingly and/or arepunctured in those REs.

A WTRU or UE may have and/or gain knowledge of PRS parameters and/ortransmission characteristics from information provided to it and may usesuch information for collision handling. For example, the WTRU or UE maygain knowledge from the E-SMLC (e.g., via LPP signaling) or from the eNB(e.g., by RRC signaling). The parameters may include any one or more ofthose described herein, as well as others.

From these and/or other parameters, the WTRU or UE may determine inwhich subframes and/or in which RBs of those subframes PRS may betransmitted in a given cell. The WTRU or UE may or may not take intoaccount PRS muting when determining in which subframes of a cell PRS maybe transmitted.

When determining whether DM-RS REs, for example ePDCCH DM-RS REs, maycollide with PRS REs in an RB of a given cell, the WTRU or UE may useone or more of the CP length for a subframe or the cell, the number ofantenna ports configured for ePDCCH transmission, the cell's physicalcell ID, and the PRS v_(shift) value which may be derived from thecell's physical cell ID, for example v_(shift)=N_(ID) ^(cell) mod6 .

Additionally, for example, for collision handling, location or antennaport mapping may be used for DM-RS REs according to an exampleembodiment. The eNB may change the placement of the DM-RS REs in RBs inwhich ePDCCH candidate(s) may be located in subframes of a cell in whichPRS may be transmitted. In subframes in which the eNB may transmit PRSin a given cell, the eNB may change the placement of DM-RS REs, such asePDCCH DM-RS REs to avoid collision with PRS REs. The eNB may change theplacement of the DM-RS REs, such as ePDCCH DM-RS REs if at least oneDM-RS RE may otherwise collide with a PRS RE. The eNB may change theplacement of the DM-RS REs, such as ePDCCH DM-RS REs, that may otherwisecollide with PRS REs.

The certain DM-RS REs whose placement may be moved may include: one ormore (e.g., which may include all) DM-RS REs that may otherwise collidewith PRS REs, one or more (e.g., which may include all) DM-RS REs thathave the same carrier frequency as DM-RS REs that may collide with PRSREs if they were not moved, and/or one or more (e.g., which may includeall) DM-RS REs in an adjacent carrier frequency to DM-RS REs that if notmoved may collide with PRS REs (e.g., if DM-RS REs in frequency X wouldcollide with PRS REs, DM-RS REs in an adjacent frequency to X may bemoved).

In subframes in which PRS may be transmitted, the interpretation ofantenna ports by the eNB with respect to DM-RS such as ePDCCH DM-RS maybe modified. The interpretation may be a function of at least one ormore of the physical cell ID of the cell, the PRS v_(shift) of the cell,the CP length (e.g., for the cell, the subframe, or normal subframe),and/or the number of antenna ports configured for ePDCCH transmission.

The placement change may be in frequency, such as an increase ordecrease in frequency for example. The placement change may or may notinclude a change in symbol. The placement change may be a function of atleast one or more of the physical cell ID of the cell, the PRS v_(shift)of the cell, the CP length (e.g., for the cell, the subframe, or normalsubframe), and/or the number of antenna ports configured for ePDCCHtransmission.

In a cell in which the eNB may transmit PRS, the eNB may change theplacement of DM-RS REs, such as ePDCCH DM-RS REs, in certain subframesto avoid or reduce collision with PRS REs in the subframes in which theeNB may transmit PRS. The certain subframes may include subframes inwhich the eNB may transmit PRS and/or may not transmit PRS, for example,the certain subframes may include all subframes. The eNB may change theplacement as described above. In this cell (e.g., the cell in which theeNB may transmit PRS), the interpretation of antenna ports by the eNBwith respect to DM-RS, such as ePDCCH DM-RS, may be modified in certainsubframes to align with a desired modification in the subframes in whichthe eNB may transmit PRS. The certain subframes may include subframes inwhich the eNB may transmit PRS and/or may not transmit PRS, for example,the certain subframes may include all subframes.

In a cell in which the eNB may or may not transmit PRS, the eNB maychange the placement of DM-RS REs, such as ePDCCH DM-RS REs, in thesubframes based on where the PRS may be placed if the cell were totransmit PRS. The eNB may change the placement, as described herein. Inthis cell (e.g., the cell in which the eNB may or may not transmit PRS),the interpretation of antenna ports by the eNB with respect to DM-RS,such as ePDCCH DM-RS, may be modified in the subframes to align withwhat would be the desired modification if the cell were to transmit PRS.

The eNB may move the DM-RS REs, or modify the antenna portinterpretation, in one or more of the ways described for ePDCCH DM-RSREs in a given subframe. The eNB may move the DM-RS REs, or modify theantenna port interpretation, for PDSCH granted by ePDCCH in thatsubframe in the same, or similar, way, for example.

In subframes in which PRS may be transmitted, the WTRU or UE may monitoror attempt to decode ePDCCH candidate(s) using a modified DM-RS pattern(e.g., which may be different from the DM-RS pattern which may be usedfor ePDCCH in subframes in which PRS may not be transmitted). In thesesubframes (e.g., subframes in which PRS may be transmitted), theinterpretation of antenna ports by the WTRU or UE with respect to DM-RSsuch as ePDCCH DM-RS may be modified. The interpretation may be afunction of at least one or more of the physical cell ID of the cell,the PRS v_(shift) of the cell, the CP length (e.g., for the cell, thesubframe, or normal subframe), and/or the number of antenna portsconfigured for ePDCCH transmission.

In one or more subframes (e.g., which may include all subframes) of acell which may transmit PRS, the WTRU or UE may monitor or attempt todecode ePDCCH candidate(s) using a modified DM-RS pattern (e.g., whichmay be different from the DM-RS pattern which may be used for ePDCCH ina cell that may not transmit PRS). In these subframes (e.g., one ormore, which may include all, subframes of a cell which may transmitPRS), the interpretation of antenna ports by the WTRU or UE with respectto DM-RS such as ePDCCH DM-RS may be modified. The interpretation may bea function of at least one or more of the physical cell ID of the cell,the PRS v_(shift) of the cell, and/or the number of antenna portsconfigured for ePDCCH transmission.

The modified DM-RS pattern and/or the antenna port interpretation may bea function of one or more of the location of the PRS RBs, the locationof the PRS REs, the physical layer cell ID of the cell, the PRSv_(shift) of the cell, the CP length (e.g., for the cell, the subframe,or normal subframe), and/or the number of antenna ports configured forePDCCH transmission.

According to an embodiment, the WTRU or UE may use a modified DM-RSpattern or antenna port interpretation for decoding PDSCH such as aPDSCH granted by ePDCCH that may use a modified DM-RS pattern or antennainterpretation. For example, the WTRU may use a modified DM-RS patternsuch as the same, or similar, pattern used for ePDCCH DM-RS, fordecoding PDSCH granted by the ePDCCH in the subframes in which ePDCCHuses a modified DM-RS pattern. In another example, the WTRU may use amodified antenna port interpretation, such as the same, or similar,interpretation used for ePDCCH DM-RS, for PDSCH granted by the ePDCCH inthe subframes in which ePDCCH uses a modified antenna portinterpretation.

Additionally, for example, for collision handling, embodiments may bedescribed for antenna port restrictions for DM-RS REs. For example, theeNB may impose antenna port restrictions in RBs in which ePDCCHcandidate(s) may be located in subframes of a cell in which PRS may betransmitted. In subframes in which the eNB may transmit PRS in a givencell, the eNB may restrict the usage of certain antenna ports for ePDCCHand/or PDSCH. Such restriction may be based on at least one of thephysical layer cell ID of the cell, the PRS v_(shift) of the cell, theCP length (e.g., for the cell, the subframe, or normal subframe), and/orthe number of antenna ports configured for ePDCCH transmission. As anexample, if antenna ports 7, 8, 9, and 10 may be configured for ePDCCHtransmission, a restriction to limit to ports 7 and 8 or ports 9 and 10may be imposed in subframes in which PRS may be transmitted and thisrestriction may be based on at least one of the physical layer cell IDof the cell, the PRS v_(shift), and/or the CP length (e.g., for thecell, the subframe, or normal subframe).

In subframes in which PRS may be transmitted, the WTRU or UE may monitoror attempt to decode ePDCCH candidate(s) using a restricted set ofantenna ports. The WTRU or UE may use a restricted set of antenna portssuch as the same, or similar, restricted set of antenna ports used forePDCCH, for PDSCH granted by the ePDCCH in the subframes in which ePDCCHuses a restricted set of antenna ports. When a restricted set of antennaports may be used, that restricted set may replace the configured orother antenna port set, for example in any of the solutions orembodiments described herein.

A different ePDCCH configuration may be implemented for certainsubframes, such as PRS subframes (e.g., for collision handling). In suchan embodiment, for a cell, there may be a different configuration forePDCCH for use in subframes in which PRS may be transmitted than forePDCCH for use in subframes in which PRS may not be transmitted. Insubframes in which PRS may be transmitted, the WTRU or UE may monitor orattempt to decode ePDCCH candidate(s) in accordance with theconfiguration for those subframes. The WTRU or UE may receive the ePDCCHconfiguration for the subframes in which PRS may be transmitted from theeNB via dedicated or broadcast signaling, which may be RRC signaling forexample. The WTRU or UE may receive one or more ePDCCH configurationsand may receive instructions, for example from the eNB, as to whichconfiguration to use and when. For example, the instruction may indicatein which subframes (e.g., subframes in which PRS may or may not betransmitted) or under what circumstances to use a certain configuration.

In subframes in which PRS may be transmitted, PRS may also be overridden(e.g., for collision handling). For example, REs, such as ePDCCH REs forexample, may override PRS REs. Override of a first signal over a secondsignal may prevent transmission of the second signal, while transmissionof the first signal may be enabled. For example, RE1 may override RE2,upon which RE1, or the signal in RE1, may be transmitted and RE2, or thesignal in RE2, may not be transmitted.

In subframes in which PRS may be transmitted, an RE may (e.g., in thecase of collision with a PRS RE) override the PRS RE. For example, suchan override may occur when one or more of the following may occur or betrue: the RE may be an ePDCCH DM-RS RE such as any ePDCCH DM-RS RE; theRE may be a certain ePDCCH DM-RS RE, for example an ePDCCH DM-RS REcorresponding to a certain antenna; the RE may be an ePDCCH DM-RS RE(e.g., any ePDCCH DM-RS RE) in ePDCCH common search space; the RE may bean RE in ePDCCH common search space such as any RE in ePDCCH commonsearch space; and/or the like.

If an RE, such as an ePDCCH RE or an ePDCCH DM-RS RE for example, mayoverride a PRS RE, a collision between the RE and the PRS RE may beremoved or avoided (e.g., since the PRS RE or the signal in the PRS REmay not be transmitted). If a collision between an RE and a PRS RE maybe removed or avoided, for example by override, the WTRU may determinethat there may be no collision between the RE and the PRS RE. Based onthis determination, the WTRU may make various decisions, such as whetheror not to monitor or attempt to decode ePDCCH candidate(s) or ePDCCHcandidates which may be located in RBs or REs in subframes in which PRSmay be transmitted in a cell.

Blind decoding (e.g., optimization thereof) may be performed (e.g., forcollision handling). For example, based on the configured ePDCCHresources, the WTRU or UE may perform a number of blind decodes, whichmay be referred to as the full set of blind decodes. In an example, whensome of the ePDCCH candidate(s) may be located in RBs which may collidewith PRS RBs in subframes in which PRS may be transmitted in a cell, theWTRU or UE may monitor or attempt to decode a subset of the configuredRBs in which ePDCCH candidates may be located. In such scenarios, theWTRU or UE may perform one or more of the following: use the full set ofblind decodes in the subset of RBs (e.g., to recover the overall decodesfor the subframe) and/or use a set of blind decodes in the subset of RBswhich may be greater than or equal to the set for these RBs as part ofthe full configuration and less than or equal to the full set for thefull configuration. For example, if the full set of RBs corresponds to Nblind decodes and a partial set corresponds to M of those N, whenattempting to decode the partial set (or only the partial set), the WTRUor UE may use W blind decodes where W may be Nor M≤W≤N.

Additionally, in embodiments (e.g., for collision handling), the eNB mayhave or gain knowledge of WTRU or UE positioning capabilities and/or ofwhich WTRUs or UEs may know about PRS transmission and/or PRSparameters. For example, the eNB may receive information from the E-SMLCor another network entity regarding WTRU or UE positioning capabilitiesand/or regarding which WTRUs or UEs may have knowledge of PRStransmission and/or PRS parameters in one or more cells. The eNB mayrequest and/or receive this and/or other information via the LPPainterface or protocol, for example. For a given or certain WTRU or UE(or WTRUs or UEs), this information may include one or more of whetherthe WTRU(s) or UE(s) may have the capability to support OTDOA, whetherPRS information has been provided to the WTRU(s) or UE(s) (e.g., by theE-SMLC or other network entity, for example, as part of positioningassistance data), whether the PRS information may have been provided fora certain cell or cells (e.g., such as cells under the control of theeNB which may be a serving cell or cells of the WTRU(s) or UE(s)), forwhich cell or cells such information may have been provided to theWTRU(s) or UE(s), and/or whether PRS information may have beensuccessfully received by the WTRU(s) or UE(s), and/or the like. The PRSinformation may include one or more of the PRS transmission subframes,BW, RBs, REs, muting information, and/or any other information relatedto PRS (e.g., PRS information described herein or parameters from whichthe enumerated information may be determined).

The E-SMLC and/or another network entity may know whether the PRSinformation has been successfully received by a WTRU or UE based onreceiving an acknowledgement (ACK) or other indication from the WTRU orUE in response to successful receipt of this information, which may havebeen provided by the E-SMLC or other network entity. If there is no ACKor other indication from a WTRU or UE in response to the E-SMLC or othernetwork entity providing PRS information, the E-SMLC or other networkentity's knowledge of WTRU or UE awareness of PRS information may beunreliable.

The WTRU or UE may also handle PRS information from one or more sources(e.g., for collision handling). For example, the WTRU or UE may receivePRS information for a cell from at least one source such as the E-SMLC,the eNB controlling the cell transmission of PRS, another cell, oranother network entity. The WTRU or UE may handle the PRS information itreceives as described herein.

Knowledge of a cell's PRS transmission information by a WTRU or UE maybe stale or unreliable, for example, if that information may have beenreceived from the E-SMLC or a network entity other than the eNB that maybe controlling or that may have knowledge of the PRS transmission. Forexample, although the eNB may inform the E-SMLC or other network entitywhen PRS transmission parameters for one or more cells changes, if theWTRU or UE receives PRS information for a cell and PRS informationchanges, for example, some time later, the PRS information known to theWTRU or UE may be incorrect. This information may be incorrect until theeNB informs the E-SMLC or other network entity of the change and/or theE-SMLC or other network entity informs the WTRU or UE.

The WTRU or UE may use (or may only use) PRS information it may receivefrom an eNB, for example for determining how to handle ePDCCH in a cell,or in PRS subframes of a cell, which may transmit PRS. The eNB may bethe eNB responsible for the PRS transmission in the cell, or another eNBwhich may provide configuration to the WTRU or UE for that cell (e.g.,as part of information provided in signaling related to handover). TheWTRU or UE may not use (or may not be permitted to use) PRS informationit may receive from another source, such as the E-SMLC or anothernetwork entity, for example, to determine how to handle ePDCCH in acell, or in PRS subframes of a cell, which may transmit PRS. This may beprovided (or beneficial) when the eNB may not be aware of which WTRUs orUEs may have acquired PRS information from another source, such as theE-SMLC or other network entity. The WTRU or UE behavior may be unknownto, or unpredictable by, the eNB if the WTRU or UE were to use theinformation received from the other source. The eNB may send differentPRS information to the WTRU or UE than what may be sent to the WTRU orUE by the E-SMLC or other network entity to achieve a certain behavior.

The WTRU or UE may use PRS information it may receive from the E-SMLC orother network entity, for example to determine how to handle ePDCCH in acell, or in PRS subframes of a cell, which may transmit PRS. If the WTRUor UE may receive PRS information for a given cell from multiple sourcesthe WTRU or UE may expect the information from the multiple sources tobe the same and behavior may be undefined if they may not be. The WTRUor UE may consider PRS information for a given cell received from an eNBto override PRS information it may have previously received from asource (e.g., any source), for example, for the purpose of ePDCCHhandling. The WTRU or UE may consider PRS information for a given cellreceived from any source to override PRS information it may havepreviously received from a source (e.g., any source), for example, forthe purpose of ePDCCH handling.

Furthermore (e.g., for collision handling), embodiments may be describedfor handling ePHICH collision with PRS. In subframes in which PRS may betransmitted, one or more of the following may apply: if ePHICH maycollide with PRS, ePHICH may override PRS; if DM-RS REs for ePHICH maycollide with PRS REs, DM-RS REs for ePHICH may override PRS REs; and/orif ePHICH REs may collide with PRS REs, ePHICH REs may be rate-matchedaround the PRS REs. The WTRU or UE may take this into account whenmonitoring or attempting to decode ePHICH.

One or more of the embodiments described herein for handling ePDCCH orePDCCH and PRS may be applied for handling ePHICH or ePHICH and PRS. Forexample, a WTRU configured for at least one of ePDCCH or ePHICH mayfallback to monitoring or attempting to decode PHICH and/or may notmonitor or attempt to decode ePHICH in subframes in which fallback maybe configured, in subframes in which ePDCCH or ePDCCH monitoring orePHICH or ePHICH monitoring may have not been configured, in subframesin which PRS may be transmitted, or in subframes in which the collisionor possibility of collision with PRS in those subframes warrants suchbehavior in accordance with one or more embodiments described herein.

Quasi-collocated antenna ports may also be provided and/or usedaccording to an embodiment. For example, the demodulation of certaindownlink channels such as PDSCH in certain transmission modes may needthe WTRU or UE to estimate the channel from reference signals such asWTRU or UE-specific reference signals (e.g., transmitted over antennaports 7 to 14). As part of such a procedure, the WTRU or UE may performfine time and/or frequency synchronization to these reference signals aswell as an estimation of certain properties related to the large-scalecharacteristics of the propagation channel.

In an embodiment, such a procedure may normally be facilitated by anassumption that another reference signal that may be measured on aregular basis such as the cell-specific reference signal may share thesame timing (e.g., and some other properties) as the WTRU or UE-specificreference signal. Such an assumption may be valid if these signals maybe physically transmitted from the same set of antennas. On the otherhand, in embodiments with geographically distributed antennas theassumption may not be valid as the WTRU or UE-specific reference signal(e.g., and the associated downlink channel) may be transmitted from adifferent point than the cell-specific reference signal. As such, theWTRU or UE may be informed via a reference signal (e.g., CSI-RS) thatmay share the same timing and/or other characteristics as a referencesignal used for demodulation. The corresponding antenna ports (e.g., twoantenna ports) may then be “quasi-collocated” such that the WTRU or UEmay assume that large-scale properties of the signal received from thefirst antenna port may be inferred from the signal received from anotherantenna port. The “large-scale properties” may include one or more ofthe following: delay spread; Doppler spread; frequency shift; averagereceived power; received timing; and the like. As described herein, anePDCCH may be demodulated using these reference signals that may betransmitted on antenna ports such as antenna ports 7-10. To exploit thepotential capacity benefit of an ePDCCH as well as area splitting gains,the ePDCCH may also be transmitted from a transmission point of a cell.To transmit the ePDCCH from a transmission point of cell, user devicesUEs may need to use and/or know one or more reference signals such as aCSI-RS that may be quasi-collocated with an antenna port used for thedemodulation of the ePDCCH. Unfortunately, the use and knowledge of suchreference symbols that may be quasi-collocated with an antenna port thatmay be used for the demodulation of the ePDCCH may be difficult asdownlink control information that may be potentially signaled tends tobe available after the ePDCCH may be decoded.

As such, systems and/or methods for providing a demodulation a referencetiming indication may be disclosed herein. For example, a singledemodulation reference timing may be provided and/or used. In such anembodiment (e.g., a first embodiment), the WTRU or UE may assume,identify, or determine that at least one quasi-collocated antenna portmay be a pre-defined antenna port (e.g., at least one of ports 0-3 onwhich cell-specific reference signals may be transmitted) and/or atleast one antenna port configured by higher layers (e.g., at least oneof ports 15-23 of one configuration of CSI-RS reference signal). Thenetwork may transmit the ePDCCH to the WTRU or UE over the sametransmission point corresponding to the pre-defined or pre-configuredquasi-collocated antenna port. The network may also transmit the ePDCCHover a different transmission point if it may know that the large-scaleproperties of a reference signal transmitted from this point may besufficiently similar to not impact demodulation performance. Forexample, in an embodiment, if antenna port 0 (CRS) may be defined to bea quasi-collocated antenna port and if the CRS may be transmitted fromnodes (including a high power node and low power nodes), the network maytransmit ePDCCH from a certain low-power node if it knows that thereceived timing of a reference signal transmitted from that low-powernode may be sufficiently close to that of the CRS.

To enable such an embodiment, the WTRU or UE may estimate at least oneproperty of at least one reference signal such as CSI-RS that may beknown by the network to be transmitted from a given transmission point.The property that may be measured may include at least one of thefollowing: received timing, average received power, frequency shift,Doppler spread, delay spread, and the like.

At least one of the above properties may be relative to the sameproperty for another pre-defined or configured reference signal. Forexample, the WTRU or UE may estimate the difference in received timingbetween the concerned reference signal and a cell-specific referencesignal (CRS). In another example, the WTRU or UE may estimate the ratio(in dB) between the averages received power of the concerned referencesignal and the CRS.

In an embodiment, to calculate the estimate, the WTRU or UE may performaveraging over more than one antenna port over which the concernedreference signal(s) may be transmitted. The WTRU or UE may also performaveraging over multiple subframes and multiple resource blocks (e.g., ina frequency domain). A new measurement type may also be defined for eachof the above-mentioned properties.

The WTRU or UE may report the measurement result for the at least oneproperty to the network using RRC message (e.g., a measurement report)or lower layer signaling (e.g., a MAC control element or physical layersignaling). Using these results, the network may determine iftransmission from a certain point may be feasible based on or takinginto account what antenna port (or reference signal) the WTRU or UEassumes, identifies, or determines to be quasi-collocated with theantenna port utilized for demodulation. For example, if the differencein timing with a CRS that the WTRU or UE may assume, identify, ordetermine to be quasi-collocated may too large, the network may transmitusing the same transmission point(s) as those used for CRS (e.g., at theexpense of a loss or splitting gain).

Additionally, in an embodiment, the WTRU or UE may trigger thetransmission of 0the measurement result(s) periodically. Alternatively,the WTRU or UE may trigger the transmission of the results when at leastone of the following events may occur. The WTRU or UE may trigger thetransmission when the difference of the property between the referencesignals becomes higher or lower than a threshold. For example, the WTRUor UE may trigger transmission of the report if the received timingdifference between a certain configured CSI-RS and the CRS may becomehigher than a threshold. The WTRU or UE may also trigger thetransmission when an absolute value of the property of the referencesignals becomes higher or lower than a threshold. For example, the WTRUor UE may trigger transmission of the report if the measured delayspread may become higher than a threshold. Such events and associatedparameters or thresholds may be configured as part of a measurementreporting configuration (e.g., reportConfig).

The network may also estimate whether some large-scale properties may besimilar or not (e.g., if the received timing may similar) by measuringuplink transmissions from the WTRU or UE such as SRS, PUCCH, PUSCH orPRACH, and the like in different reception points coinciding withtransmission points potentially used for downlink transmissions.

Multiple demodulation reference timing may be provided and/or used. Insuch an embodiment (e.g., a second embodiment), to receive ePDCCH and/orPDSCH based on a WTRU or UE-specific reference signal (e.g., antennaport 7˜14), at least one of following reference signals may be used toindicate the demodulation reference timing for a WTRU or UE: CSI-RS,CRS, PRS, and the like.

If a WTRU or UE may be provided or informed about a demodulationreference timing with a reference signal, a WTRU or UE demodulationprocess including FFT timing and channel estimation filter coefficientmay follow the reference signals. For example, if there may be twoCSI-RS configured for a WTRU or UE such as CSI-RS₁ and CSI-RS₂ and theWTRU or UE may report CSI for both CSI-RS configurations, FFT timing andfine time and/or frequency synchronization for PDSCH demodulation mayfollow one of two CSI-RS configurations according to the demodulationreference timing indication.

Alternatively, if a WTRU or UE informed about the demodulation referencetiming with a reference signal, the PDSCH demodulation procedure may bedifferent according to the type of reference signal based on one or moreof the following.

If a CSI may be used for reference timing, the FFT timing and channelestimation filter coefficient for the CSI-RS may be used for PDSCHdemodulation. For example, a WTRU or UE may assume, identify, ordetermine that the PDSCH and/or WTRU or UE-specific demodulation RS(e.g., antenna ports 7˜14) may be transmitted from the samequasi-collocated antenna ports. As such, if a WTRU or UE may beconfigured to monitor ePDCCH (e.g., for each PRB set), the WTRU or UEmay assume, identify, or determine that a first set of antenna ports(e.g., 15-22) may be associated with or correspond to the CSI-RSinformation and/or may identify a mapping for the PDSCH and otherantenna ports (e.g., 7-14 or other ports) may be quasi co-located withrespect to parameters such as Doppler shift, Doppler spread, averagedelay, delay spread, and the like as described above.

If a CRS may be used for reference timing, the FFT timing and channelestimation filter coefficients for the CRS may be used for PDSCHdemodulation. Alternatively, a time and/or frequency offset for the CRSmay be provided for PDSCH demodulation. If a WTRU or UE may be informedabout the offsets, the WTRU or UE may apply the offsets from the CRS. Inexample embodiments, at least one of following offsets may be provided:FFT timing offset (ΔFFT), time offset (ΔT), frequency offset (ΔF), andthe like.

If a PRS may be used for reference timing, the similar WTRU or UEbehavior as either CSI-RS or CRS may be applied in such an embodiment.

In an embodiment, the demodulation reference timing may be informed to aWTRU or UE in implicit or explicit manner. Also, a single demodulationreference for a given time window (e.g., a subframe or radio frame) maybe applied or multiple demodulation reference may be used.

An implicit demodulation reference timing indication may be providedand/or used. In such an embodiment (e.g., a first solution), thedemodulation reference timing may be tied with ePDCCH and/or PDCCHresources and may be implicitly informed to a WTRU or UE. Since a DCIshould be received to demodulate PDSCH, the demodulation timingreference may be inferred from the location of ePDCCH and/or PDCCHresources where a WTRU or UE may receive the DCI. At least one offollowing methods may be used to implement an ePDCCH and/or PDCCHresource based indication.

In one embodiment, a WTRU or UE-specific search space may be split totwo or more number of subsets and each subset may be tied with aspecific demodulation timing reference. For example, within a WTRU orUE-specific search space, the total blind decoding attempts 2N_(blind)may be split to two subsets (subset₁ and subset₂) and each subset mayinclude exclusive Nb_(blind) decoding attempts where each subset may betied with a different demodulation timing reference. For example,subset' may be tied with CSI-RS₁ and subset₂ may be tied with CSI-RS₂.As such, in an embodiment, if a WTRU or UE may receive a DCI for PDSCHin the subset', the WTRU or UE may assume, identifier, or determine thatthe PDSCH may be transmitted in the same transmission point withCSI-RS₁.

Additionally, as described herein, for an ePDCCH WTRU or UE-specificsearch space, the search space subset may be tied with the demodulationtiming reference. Therefore, when a WTRU or UE may perform blinddecoding for ePDCCH, the WTRU or UE may assume, identify, or determinethat the subset₁ and subset₂ may be transmitted from the sametransmission point with CSI-RS₁ and CSI-RS₂ respectively. In anotherembodiment, as described herein, if a WTRU or UE may receive a DCI viaePDCCH, the WTRU or UE may assume, identify, or determine that thecorresponding PDSCH may be transmitted from the same transmission pointwith ePDCCH. Furthermore, for an ePDCCH common search space (e.g., asdescribed herein), a WTRU or UE may assume, identify, or determine thatthe ePDCCH may be transmitted from the same transmission point with CRS.

As such, in embodiments, if the WTRU or UE may be configured to monitorePDCCH (e.g., for each PRB set), the WTRU or UE may use a parameter setindicated by a higher layer parameter such as CSI-RS for determiningmapping information and/or antenna port quasi co-location (e.g.,ePDCCH).

According to another embodiment (e.g., a second solution), thedemodulation antenna ports may be tied with demodulation timingreference. If antenna ports 7˜10 may be available for ePDCCH and/orPDSCH demodulation, multiple pairs of quasi-collocated ports may bepre-defined. For example, a WTRU or UE may assume, identify, ordetermine that the antenna ports {7, 8} and {9, 10} may bequasi-collocated, where the quasi-collocated pair {7, 8} and {9, 10} maybe tied with CSI-RS₁ and CSI-RS₂, respectively. In such an embodiment, aWTRU or UE may also assume, identify, or determine that the demodulationtiming reference for antenna port-7 may be the same as antenna port-8.Alternatively, scrambling ID (n_(SCID)) may be also tied withdemodulation timing reference assuming that multiple n_(SCID) may beused. If n_(SCID)=0 and n_(SCID)=1 may be used, a WTRU or UE may assume,identify, or determine that n_(SCID)=0 may be tied with CSI-RS₁ andn_(SCID)=1 may be tied with CSI-RS₂ for example. According to anotheralternative, the n_(SCID) may be tied with antenna ports. For example,n_(SCID)=0 may be used for antenna ports {7, 8} and n_(SCID)=1 may beused for antenna ports {9, 10}. As such, a WTRU or UE may assume,identify, or determine that n_(SCID)=0 may be used when the WTRU or UEmay demodulate signals based on antenna ports {7, 8}, and n_(SCID)=1 maybe used when the WTRU or UE may demodulate signals based on antenna port{9, 10}. The antenna ports to n_(SCID) mapping may be configured atleast one of following: the antenna port to n_(SCID) mapping may bepredefined where, in such an embodiment, the quasi-collocated antennaports may have the same n_(SCID); the antenna port to n_(SCID) mappingmay be configured by broadcasting channels or higher layer signalling;and the like.

The scrambling sequence may be initialized byc _(init)=(└n _(s)/2┘+1)·(2N _(ID) ^(X)+1)·2¹⁶ +n _(SCID)where in c_(init), N^(X) _(ID) may be higher layer configurable value orpredefined value as physical cell ID.

In another embodiment (e.g., a third solution), downlink resources maybe tied with demodulation timing reference. In such an embodiment,according to the downlink resource position for E-PDSCH and/or PDSCH, aWTRU or UE may infer the demodulation reference timing. The downlinkposition may include at least one of following: a subset of downlinksubframe(s) and/or PRBs that may be configured to use a specificdemodulation reference time. Optionally, the reference time may be usedfor the demodulation of antenna ports 7˜14. Otherwise, CRS may be usedas the reference timing.

In yet another embodiment (e.g., a forth solution), the demodulationreference timing may be defined with a time relation with CSI-RS and CSIfeedback. The WTRU or UE behaviors in such an embodiment may be definedby at least one of the following. A WTRU or UE may assume, identify, ordetermine that the PDSCH may be transmitted from the transmission pointwith CSI-RS_(k) if the latest CSI-RS WTRU or UE received may be theCSI-RS_(k). In such an embodiment, a subframe offset may be additionallybe defined such that a WTRU or UE may assume, identify, or determine thedemodulation reference timing may be changed after the number of offsetsubframe.

Additionally, a WTRU or UE may assume, identify, or determine that thePDSCH may be transmitted from the transmission point with CSI-RS_(k) ifthe latest CSI feedback WTRU or UE report may be based on theCSI-RS_(k), where the latest CSI feedback may be at least one offollowing: aperiodic CSI reporting; periodic CSI reporting with PMI/CQIwhere if the latest CSI reporting type was RI, the demodulationreference timing may be kept unchanged; periodic CSI reporting withPMI/CQI/RI; the offset subframe that may be applied such that thedemodulation reference timing may be changed after the number of offsetsubframe; and the like.

An implicit indication of PDSCH demodulation information may also beprovided and/or used as described herein. For example, as describedherein, methods or procedures may be used to determine, for example,PDSCH demodulation information that may be used by the WTRU or UE upondecoding PDSCH in a subframe. The PDSCH demodulation information mayinclude one or more of the following. For example, the PDSCHdemodulation information may include a reference signal (e.g., orantenna port) that may be assumed as quasi-collocated to referencesignals (e.g., or antenna ports) that may be used for PDSCH demodulation(e.g., including an index to a non-zero-power CSI-RS resource). ThePDSCH demodulation information may also include at least one parameterthat may be used to determine a location of resource elements (RE) onwhich PDSCH may be transmitted, or on which PDSCH may not be transmitted(e.g., for rate matching purposes), such as one or more of thefollowing: at least one parameter indicating the location of CRS portson which PDSCH may not be transmitted (e.g., a number of CRS ports, aCRS frequency shift); a MBSFN configuration; at least one parameterindicating the location of zero-power CSI-RS on which PDSCH may not betransmitted such as a configuration of zero-power CSI-RS; an indicationof the PDSCH starting symbol; at least one parameter indicating thelocation of a non-zero-power CSI-RS on which PDSCH may not betransmitted; at least one parameter indicating the location of resourceelements that may be used for interference measurement resources; andthe like. Additionally, the PDSCH demodulation information may furtherinclude a scrambling identity that may be used to determine ademodulation reference signal

In one example embodiment (e.g., an example method), the WTRU or UE maydetermine PDSCH demodulation information based on the identity of areference signal (e.g., such as CRS or CSI-RS) that may be assumed asquasi-collocated to the reference signal that may be used fordemodulating the ePDCCH including the assignment (e.g., controlinformation) for this PDSCH. In such an embodiment (e.g., method), thenetwork may use the same transmission point for the ePDCCH and the PDSCHthat may be signaled by the same ePDCCH. Additionally, since some of thePDSCH demodulation information may be tied (e.g., often closely tied) tothe used transmission point, such information may be derived implicitlyfrom the reference signal that may be assumed to be quasi-collocated.

For example, if the WTRU or UE may determine that a certainnon-zero-power CSI-RS resource may be collocated to the reference signalthat may be used for the ePDCCH, the WTRU or UE may assume that the samenon-zero-power CSI-RS resource may correspond to a reference signalcollocated to the reference signals that may be used for demodulatingthe PDSCH. Additionally, the index of this non-zero-power CSI-RSresource may indicate (e.g., possibly in combination with anotherindication of the downlink control information) a set of parameters thatmay determine PDSCH demodulation information that may be configured byhigher layers.

In another embodiment (e.g., example method), the WTRU or UE maydetermine PDSCH demodulation information based on, for example, aproperty (e.g., another property) of the ePDCCH including the downlinkcontrol information that may be applicable to this PDSCH such as asearch space, or ePDCCH set in which ePDCCH may have been decoded, theaggregation level, whether the corresponding ePDCCH set may bedistributed or localized, and the like.

In example embodiments, the use of one or more of the above embodimentsor methods may be conditioned on at least one of the following: anindication from higher layers that PDSCH demodulation information may beobtained using the method; an indication from the downlink controlinformation applicable to this PDSCH (e.g., the method may be applied ifone of a specific subset of values of a new or existing field may bereceived and for other values of this field, the WTRU or UE may obtainthe PDSCH demodulation information based on the value of the field); aRRC configuration, for example, based on the configured DCI format, theconfigured transmission mode (e.g., may be applicable to TM10), theconfigured behavior for determining ePDCCH collocation reference signal(e.g., the method may apply if ePDCCH quasi-collocated reference signalmay be obtained based on the ePDCCH set in which ePDCCH may be decoded,whether the non-zero-power CSI-RS resources configured for each ePDCCHset for the purpose of determining quasi-collocation may be different;and the like.

An explicit demodulation reference timing indication may be providedand/or used. In such an embodiment (e.g., a first solution), thedemodulation reference timing may be indicated or included in a DCI forPDSCH. For example, indication bit(s) may be explicitly located in aDCI. As such, a WTRU or UE may be informed which demodulation referencetiming may be used for corresponding PDSCH demodulation. Alternatively,the demodulation reference timing may be informed to a WTRU or UE viahigher layer signalling (e.g., RRC, MAC control element, and the like).

In another such embodiment (e.g., a second solution), the demodulationreference timing may be indicated via a specific ePDCCH and/or PDCCHsuch that the demodulation reference timing may be changed from asubframe to another in a WTRU or UE-specific manner. In such anembodiment, the ePDCCH and/or PDCCH may be use at least one offollowing: an ePDCCH and/or PDCCH may trigger one of the demodulationreference timings and the triggered demodulation reference timing may bevalid for a time window where the time window may be pre-defined orconfigured by higher layer signalling; an ePDCCH and/or PDCCH maytrigger one of the demodulation reference timings and it may be validunless a different demodulation reference timing may be triggered; anePDCCH and/or PDCCH may be used for activation/de-activation to indicatethe demodulation reference timing.

WTRU or UE blind decoding attempts for multiple demodulation referencetiming may also be provided and/or used according to exampleembodiments. For example, without demodulation reference timinginformation, a WTRU or UE may blindly attempt multiple demodulationreference timing at the receiver. In such an embodiment, a WTRU or UEmay demodulate ePDCCH and/or PDSCH with each possible demodulationreference timing candidate. For example, if two CSI-RS may be configuredfor a WTRU or UE and the WTRU or UE may report CSIs for both CSI-RSconfigurations, the WTRU or UE may demodulate ePDCCH and/or PDSCH withboth CSI-RS configurations.

Although the terms UE or WTRU may be used herein, it may and should beunderstood that the use of such terms may be used interchangeably and,as such, may not be distinguishable. Additionally, for the enhancedphysical downlink control channel described herein, ePDCCH, EPDCCH,and/or ePDCCH may be used interchangeably.

Although the terms legacy PDCCH or PDCCH may be used herein to indicatethe Rel-8/9/10 PDCCH resources, it may and should be understood that theuse of such terms may be used interchangeably and, as such, may not bedistinguishable. Additionally, PDCCH and DCI may be used interchangeablyas a meaning of downlink control information transmitted from to eNB toa WTRU or UE.

Furthermore, although features and elements may be described above inparticular combinations, one of ordinary skill in the art willappreciate that each feature or element can be used alone or in anycombination with the other features and elements. In addition, themethods described herein may be implemented in a computer program,software, or firmware incorporated in a computer-readable medium forexecution by a computer or processor. Examples of computer-readablemedia include electronic signals (transmitted over wired or wirelessconnections) and computer-readable storage media. Examples ofcomputer-readable storage media include, but may not be limited to, aread only memory (ROM), a random access memory (RAM), a register, cachememory, semiconductor memory devices, magnetic media such as internalhard disks and removable disks, magneto-optical media, and optical mediasuch as CD-ROM disks, and digital versatile disks (DVDs). A processor inassociation with software may be used to implement a radio frequencytransceiver for use in a WTRU, UE, terminal, base station, RNC, or anyhost computer.

What is claimed:
 1. A method implemented by a wireless transmit/receiveunit (WTRU) for utilizing an enhanced physical downlink control channel(ePDCCH), the method comprising: the WTRU receiving a configuration, theconfiguration (i) defining a plurality of ePDCCH resource sets; (ii)defining a demodulation reference signal (DM-RS) scrambling sequenceinitialization parameter for each of the plurality of ePDCCH resourcesets, and (iii) indicating a demodulation timing reference informationassociated with each of the plurality of ePDCCH resource sets; the WTRUmonitoring at least one search space associated with each of theplurality of ePDCCH resource sets, wherein the at least one search spaceexcludes time and frequency resources occupied by DM-RSs of DM-RSsequences initialized with the DM-RS scrambling sequence initializationparameters for the corresponding ePDCCH resource sets; and the WTRUreceiving at least one ePDCCH transmission via at least one of theplurality of ePDCCH resource sets.
 2. The method of claim 1, wherein thedemodulation timing reference information comprises information to beused for determining a demodulation timing reference, wherein thedemodulation timing reference information comprises a first channelstate information reference signal (CSI-RS) associated with a firstePDCCH, and a second CSI-RS associated with a second ePDCCH.
 3. Themethod of claim 1, wherein the demodulation timing reference informationcomprises an indication of a pair of antenna ports, wherein the pair ofantenna ports is quasi co-located for ePDDCH processing.
 4. The methodof claim 3, wherein the pair of antenna ports are each associated with acommon channel state information reference signal (CSI-RS).
 5. Themethod of claim 3, wherein the WTRU assumes that the quasi co-locatedpair of antenna ports have a common Doppler shift, Doppler spread,average delay, and delay spread.
 6. The method of claim 1, wherein eachePDCCH resource set is associated with a different network transmissionport.
 7. The method of claim 1, wherein the at least one search space isa WTRU-specific search space.
 8. A wireless transmit/receive unit (WTRU)comprising: a processor configured to: receive a configuration, theconfiguration (i) defining a plurality of enhanced physical downlinkcontrol channel (ePDCCH) resource sets; (ii) defining a demodulationreference signal (DM-RS) scrambling sequence initialization parameterfor each of the plurality of ePDCCH resource sets; and (iii) indicatingdemodulation timing reference information associated with each of theplurality of ePDCCH resource sets; monitor at least one search spaceassociated with each of the plurality of ePDCCH resource sets, whereinthe at least one search space excludes time and frequency resourcesoccupied by DM-RSs of DM-RS sequences initialized with the DM-RSscrambling sequence initialization parameters for the correspondingePDCCH resource sets; and receive at least one ePDCCH transmission viaat least one of the plurality of ePDCCH resource sets.
 9. The WTRU ofclaim 8, wherein the demodulation timing reference information comprisesinformation to be used for determining a demodulation timing reference,wherein the demodulation timing reference information comprises a firstchannel state information reference signal (CSI-RS) associated with afirst ePDCCH, and a second CSI-RS associated with a second ePDCCH. 10.The WTRU of claim 8, wherein the demodulation timing referenceinformation comprises an indication of a pair of antenna ports, whereinthe pair of antenna ports is quasi co-located for ePDCCH processing. 11.The WTRU of claim 10, wherein the pair of antenna ports are eachassociated with a common channel state information reference signal(CSI-RS).
 12. The WTRU of claim 10, wherein the WTRU assumes that thequasi co-located pair of antenna ports have a common Doppler shift,Doppler spread, average delay, and delay spread.
 13. The WTRU of claim8, wherein each ePDCCH resource set is associated with a differentnetwork transmission point.
 14. The WTRU of claim 8, wherein the atleast one search space is a WTRU-specific search space.